FilterKing.com: from “which filter?” to a subscription shoppers choose
An independent review of the homepage, product page, category page, search and cart — tested for speed and accessibility, benchmarked against Filterbuy and Nordic Pure — with a clickable redesign concept and developer-ready specs.
Corey Frons · November 10, 2026
Fast, complete, and asking for trust it hasn't earned yet
Filter King has the hard parts right — every size, free 1–2 day shipping, a 30-day money-back guarantee and pages that pass Core Web Vitals. But the product page preselects a subscription and shows prices shoppers have reason to doubt. The fixes are mostly defaults, labels and data, not a rebuild.
Five things to fix first
Stop preselecting the subscription
"Subscribe & save 5%" is checked by default, and the phone bar shows $45.54 with no word "subscription". Filterbuy and Nordic Pure default to one-time.
Fix the price ladders
12+ MERV 13 filters cost $8.08 each, more than the 6-pack's $7.99. Two Carbon filters ($43.98) cost more than four ($34.28).
Say what "74% OFF" means
It compares a 6-pack with six single filters at $31.13 each — a struck-through $186.78 that almost no one pays.
Size finder in the first phone screen
It starts 1.2 screens down. "Shop by MERV rating" starts 6.6 screens down, below 100+ size links.
One number, one name
Five different review and customer counts, and MERV 13 is "Ultimate" on the homepage but "Superior" on the product page and box.
The live site, and the fix
Three moments every shopper hits, captured on filterking.com on November 10, 2026, next to the same moment in the concept.
How to buy: a subscription by choice
Live, the subscription is preselected and the sticky bar's icon-only button adds it at $45.54 without saying so. Rivals default to one-time, and state auto-renewal laws expect a clear yes.
The concept selects one-time, makes auto-delivery an explicit option with its schedule, and names what the bar's button does.
Price ladder: more should never cost more
On 16x25x1 MERV 13, the 12+ tier costs $8.08 a filter, above the 6-pack's $7.99; on Carbon, two filters cost more than four. The badges call each tier a percentage "OFF".
The concept shows only tiers whose price falls, states each saving against buying one, and sends 12+ to bulk pricing until the data is fixed.
Homepage: the finder first
Live, the first phone screen is a photo; the size finder starts 1.2 screens down, and "Shop by MERV rating" sits below a 4,000 px wall of size links.
The concept puts the labeled finder, the most-bought sizes and four proof tiles in the first screen, with shopping by need right after.
Phone screens rendered from the live HTML at 390 × 844 px; desktop at 1568 px. Prices are for 16x25x1.
16 findings, ranked by how much they get in a shopper's way
Must fix = blocks the purchase, misstates a price or risks a legal or accessibility complaint. Should fix = adds doubt or work. Nice to have = polish.
| # | Priority | Where | Problem | Why it matters | Fix |
|---|---|---|---|---|---|
| 1 | Must fix | Product page, desktop + phone | "Subscribe & save 5%" is preselected; the phone's sticky bar shows the subscription total ($45.54) with no mention of a subscription | Shoppers can start a recurring order without choosing one; cancellations and refunds follow, and state auto-renewal laws (e.g. California's) require clear consent — worth a legal review | Default to one-time; subscription as an explicit choice; sticky bar says "Every 3 months · $45.54" when chosen |
| 2 | Must fix | Product price ladders | 16x25x1 MERV 13: 12+ costs $8.08 each vs $7.99 for 6+. Carbon: 2 filters cost $43.98, 4 cost $34.28 | Buying more costs more; shoppers who notice stop trusting every price | Fix the tiers; an automated check that per-filter price falls as quantity rises |
| 3 | Must fix | Product offer badge | "74% OFF" and a struck-through $186.78 compare a 6-pack with six single filters at $31.13 | A reference price almost no one pays reads as a fake sale and invites scrutiny under the FTC's pricing guides | "$7.99 each in a 6-pack — 74% less than buying one"; no strike-through |
| 4 | Must fix | Phone homepage | The size finder starts 1.2 screens down and its button 1.7 screens down; a stock photo fills the first screen | Finding your size is the only task that matters on arrival | Width × length × depth and "Find my filter" in the first screen |
| 5 | Must fix | Homepage size grid | 100+ size links (580 on the page with menus) push "Shop by MERV rating" to 6.6 screens and reviews to 10.5 screens on a phone | Shoppers who don't know their size scroll past a wall; quality comes too late | The 12 most-bought sizes + "All sizes"; MERV choice under the finder |
| 6 | Must fix | Site-wide | Size-finder selects unlabeled; sticky cart button has no name; savings text fails contrast (3.3:1 green, 3.8:1 grey); white on the red Add to cart is 3.4:1 | Screen-reader and low-vision shoppers can't finish the main flow | Label selects, name the button, darken green, grey and red to 4.5:1 |
| 7 | Should fix | Homepage + product page | Five counts: 26,004 customers, 10,000+ homeowners, 4.6★ from 5,243 and 4.5★ from 4,314 (unlabeled), 4.8★ from 159 on every quality | Inconsistent proof reads as made up, even when each number is real | One sourced headline number; label sources; ratings per product |
| 8 | Should fix | Tier names | MERV 13 is "Ultimate" on the homepage, "Superior" on the product page and box; "Freedom Filters MERV 8" sits beside MERV 8 unexplained | Shoppers can't tell whether two names are two products | One name per tier everywhere; explain Freedom in a line |
| 9 | Should fix | Desktop homepage | A $10-off popup covers the page within seconds, beside "save up to 75%", 5% auto-delivery and % OFF badges | Four offers compete; none reads as the deal | One offer per moment; popup after engagement, never on product pages |
| 10 | Should fix | Choosing a MERV | No shopping by need (allergies, pets, smoke); Nordic Pure has "Air concern" in its top menu | Most shoppers know their problem, not their MERV number | Need tiles that map to MERV 8/11/13/Carbon; a "Which filter?" helper |
| 11 | Should fix | Category pages | The 1-inch page is a finder and size links — no prices, qualities or product cards | Shoppers open a size just to learn the price | "From $X" per size; a quality filter |
| 12 | Should fix | Search | "16 x 25" leads with 25x16x4 (16x25x1 is 6th); "merv 13" leads with 9x12x1; "return policy" finds nothing | Common sizes and help answers are hard to reach | Rank by sales; include help and guide pages |
| 13 | Should fix | Structured data | The MERV 11 page's Product data carries SKU "FK16x25x1-M13" and lists viruses, a MERV 13 claim | Search engines may show the wrong product details | SKU and description generated per quality |
| 14 | Nice to have | Buttons | Three primary colors: red Add to cart, navy Find filter, green "Shop air filters" in the empty cart | Mixed signals for the main action | One primary color |
| 15 | Nice to have | Copy | Typo "filration" on the MERV 11 card; "Shop by brand" copy speaks to professionals on a homeowner page | Small errors chip at a quality brand | Proofread; write for homeowners |
| 16 | Nice to have | Speed headroom | Pages pass Core Web Vitals, but server response is 1.0–1.2 s (Google's "good" is 0.8 s) and the homepage makes 245 requests to 39 hosts | Headroom shrinks as more tags arrive | Edge-cache HTML; audit third-party tags |
Speed is a strength; the problems are prices and defaults
Both Filter King pages pass Core Web Vitals for real users, while Filterbuy, Nordic Pure and Discount Filters fail. The measurable problems sit on the product page's prices and defaults, not its load time.
Speed — mobile, PageSpeed Insights
Real-user figures are Chrome UX Report data for the latest 28 days. Lighthouse scores are one lab run on an emulated mid-range phone over slow 4G.
| Page | Real users: LCP · INP · CLS | Core Web Vitals | Lighthouse: Perf · Access. · Best pr. · SEO |
|---|---|---|---|
| Filter King home | 2.2 s · 128 ms · 0.01 | Pass | 56 · 82 · 96 · 100 |
| Filter King 16x25x1 MERV 11 | 2.1 s · 146 ms · 0.01 | Pass | 63 · 88 · 96 · 100 |
| Filterbuy home | 1.6 s · 312 ms · 0 | Fail — INP | 28 · 100 · 54 · 100 |
| FiltersFast home | 1.6 s · 122 ms · 0.04 | Pass | 20 · 90 · 54 · 77 |
| Nordic Pure home | 2.5 s · 104 ms · 0 | Fail — LCP | 28 · 88 · 73 · 100 |
| Discount Filters home | 2.1 s · 104 ms · 0.26 | Fail — CLS | 19 · 89 · 73 · 92 |
The lab run shows a 6.9 s homepage LCP and 1,280 ms of blocking time on the product page — the headroom is in third-party scripts, not the site's own code.
Product page
The quality → quantity → how-to-buy flow is clear, and a sticky bar keeps the total in view on phones. But Subscribe & save is preselected, and two price ladders run the wrong way (findings 1–3).
Search
Understands actual sizes — "15.5 x 24.5" finds the 24.5x15.5x1. Ranking is weak: "16 x 25" leads with 25x16x4, "merv 13" with 9x12x1, and "return policy" offers only "Create a custom size filter".
Category page
The 1-inch page is a size finder and a list of size links: no prices, qualities or product cards to compare.
Cart and checkout
The cart was empty and I don't add items to carts, so checkout wasn't tested. Worth checking next: whether the preselected subscription carries into checkout, and how it's disclosed there.
The gaps sit on the main flow
Lighthouse scores the homepage 82 and the product page 88. Focus is visible and product images carry alt text; the misses are on the size finder, the prices and the cart button.
| # | Issue | Where | WCAG | Severity | Fix |
|---|---|---|---|---|---|
| A1 | Size-finder selects have no labels — 4 unlabeled form elements on the homepage, 5 on the product page | Size finder | 1.3.1, 3.3.2 | Major | A label on each select ("Width, inches") |
| A2 | The sticky phone cart button has no text or accessible name | Product page, phone | 4.1.2 | Major | "Add 6 filters to cart, $47.94" |
| A3 | Savings % in green (3.3:1); "You save" and struck prices in grey (3.8:1); white on red Add to cart (3.4:1) | Product page | 1.4.3 | Major | Green #15803D, grey #595959, red #C8281C |
| A4 | ARIA roles missing required attributes (5); links without a name | Homepage | 4.1.2, 2.4.4 | Major | Fix the flagged roles; name icon links |
| A5 | Iframes without a title (1 on home, 3 on product) | Chat and review widgets | 4.1.2 | Minor | Title each frame |
| A6 | MERV option buttons 32 px tall; language switcher 19 px | Product page, header | 2.5.8 (2.2) | Minor | 44 px tall options |
Not yet tested with VoiceOver or NVDA, or at 200% zoom.
Only Filter King preselects the subscription
Filterbuy and Nordic Pure both default to one-time. Filter King's 5% subscription discount ties Filterbuy's and is half of Nordic Pure's 10%.
| Brand | Default purchase | Subscription | 6-pack, 16x25x1 | Review proof | Shop by need | First-visit popup |
|---|---|---|---|---|---|---|
| Filter King | Subscribe preselected | 5% off | MERV 8 $44.94 · MERV 11 $47.94 | Five different counts | No | $10 off, desktop |
| Filterbuy | One-time | 5% off | MERV 8 $43.98 | "85K+ Reviews"; 1,816 on the size page | "Help me choose" link | 10% email offer |
| Nordic Pure | One-time | 10% off | MERV 12 $57.99 | 5.0★ from 12 | "Air concern" in the top menu | Subscribe & save 10% |
Product pages for 16x25x1 compared live on November 10, 2026. FiltersFast and Discount Filters were speed-tested only. All three lead with a size grid, so the fix is to shrink Filter King's, not drop it.
Say what the price is compared with
| Element | Today | Recommended | Why |
|---|---|---|---|
| Offer badge | 74% OFF | $7.99 each in a 6-pack — 74% less than buying one | Names the comparison |
| How to buy | Subscribe & save 5% (preselected) | One-time (selected) · Auto-delivery every 3 months, 5% off — pause, skip or cancel anytime | Consent is a choice, not a default |
| Phone sticky bar | Totals $45.54 [cart icon] | 6 filters · One-time · $47.94 · Add to cart | Says what the tap does |
| Hero | HVAC air filters built to perform | Your exact filter size, delivered when you need it | Leads with the job and the delivery benefit |
| Tier names | Standard · Advanced · Ultimate / Superior · Odor Eliminator | Standard · Advanced · Superior · Odor control | One name per tier, matching the box |
| Popup | Would you like to receive $10 OFF your first purchase? Yes / No | Get $10 off your first order · Email me the code / No thanks | Buttons say what happens |
| Delivery | Order within 6h 2min and receive it by Wednesday, November 11 | Free delivery by Wed, Nov 11 if you order in the next 6 h | Leads with the date and "free" |
Four screens, built in Filter King's own look
The same navy, red and Poppins as the live site — reordered so the size comes first, prices say what they're compared with, and auto-delivery is something shoppers choose. The product pages are clickable: switch quality, pack size and how you buy, and every price and label follows.
Desktop versions: homepage and product page — best on a laptop.
What the concept changes
| Finding | In the concept |
|---|---|
| #1 Preselected subscription | One-time selected; auto-delivery as a labeled option with its schedule; the sticky bar names the mode and the action |
| #2 Price ladders | Only 1, 4 and 6 packs, whose live per-filter price falls; 12+ linked to bulk pricing |
| #3 "74% OFF" | "$7.99 each in a 6-pack — 74% less per filter than buying one"; no strike-through |
| #4, #5 First phone screen | Labeled finder, most-bought sizes and proof tiles above the fold; 12 sizes instead of 100+ |
| #6 Accessibility | Labeled selects, named buttons, 44 px targets, darker red, green and grey |
| #7, #8 Proof and names | One review number on each page; Standard · Advanced · Superior · Odor control everywhere |
| #10 Shop by need | Everyday dust, pets, allergies and smoke tiles mapped to MERV 8, 11, 13 and Carbon |
Filters are drawn placeholders — real Filter King photography drops into the same frames. Prices, ratings and specs are from filterking.com on November 10, 2026.
Defaults and data first, templates next
The first column needs only settings, data and copy, so it can ship this week. Layout changes follow in 30–60 days.
This week — settings, data, copy
- One-time by default; label the sticky bar (#1)
- Fix the ladders; add the per-filter check (#2)
- Reword the badge; drop the strike-through (#3)
- Label the selects, name the button, darken the colors (#6)
- One review number, one name per tier (#7, #8)
30–60 days — templates
- Finder in the first phone screen; a 12-size grid (#4, #5)
- Need tiles and a "Which filter?" helper (#10)
- Prices on category pages (#11)
- Popup after engagement, not on arrival (#9)
90+ days — platform
- Search ranked by sales, with help pages (#12)
- Structured data per quality (#13)
- Edge-cached HTML and a tag audit (#16)
Judge the subscription on retention, not sign-ups
A one-time default will lower subscription sign-ups at first. The test that matters is how many subscribers are still active at 90 days, and total revenue per visitor. Filter King already runs Convert experiments, so each change can ship as an A/B test.
| Test | Change | Primary metric | Guardrail | Window |
|---|---|---|---|---|
| A | One-time default + labeled subscription | Subscribers active at 90 days | Revenue per visitor | 4 weeks + 90-day read |
| B | Opt-in subscription at 5% vs 10% | Opt-in share of orders | Margin per order | 4 weeks |
| C | Plain per-filter savings, no strike-through | Product page add-to-cart rate | Average pack size | 2 weeks |
| D | Finder in the first phone screen + 12-size grid | Home → product page rate on phones | Search use | 3 weeks |
| E | Need tiles + "Which filter?" helper | MERV 11/13 share of orders | Return rate | 4 weeks |
What a small lift on phones is worth
Put in your own numbers to size the upside of the phone fixes — the starting values are examples, not Filter King data.
How this was done
I reviewed filterking.com live in Chrome at desktop width and at 390 px on November 10, 2026: the homepage, the 16x25x1 product page in all four qualities, the 1-inch category page, search, the cart and the menus. I checked labels, contrast and tap targets in the page, ran PageSpeed Insights on Filter King and five rivals, and compared Filterbuy's and Nordic Pure's 16x25x1 pages side by side. Findings are ranked by how much they get in a shopper's way; accessibility is measured against WCAG 2.1 AA.
Not tested: checkout or a filled cart (I don't add items to carts), screen readers, 200% zoom, and the popup on phones. The synthesis is built from audit evidence; analytics and shopper sessions would turn its hypotheses into measurements.