---
title: "Reviews — 16 3/8 x 21 1/2 x1 air filter - Flapen"
canonical_url: "https://flapen.com/research/us/tools-home-improvement/16-3-8-x-21-1-2-x1-air-filter/reviews"
last_updated: "2026-08-08T11:55:33.678Z"
locale: en
meta:
  description: "Niche score 54/100 · $302K/yr market · 42K searches/yr. Brand-locked demand (top 5 brands take 94% of clicks) keeps it on the watch list. Data updated Jul 2026."
  "og:description": "Niche score 54/100 · $302K/yr market · 42K searches/yr. Brand-locked demand (top 5 brands take 94% of clicks) keeps it on the watch list. Data updated Jul 2026."
  "og:title": "Reviews — 16 3/8 x 21 1/2 x1 air filter - Flapen"
---

# **16 3/8 x 21 1/2 x1 air filter**

**Worth a look**

Shows searches that convert (15.2% search→purchase), but brand-locked demand (top 5 brands take 94% of clicks) keeps it on the watch list.

Market size 51Growth 62Conversion 97Competition 25Returns 83Price range 95Avg price 94Brand share 14Review moat 45Quality gap 20

**Conversion**

**Incredible****15.2%**

search→purchase rate — share of searches ending in a sale

**Price range**

**Incredible****$32.71–$63.36**

cheapest to priciest tracked listing — scored on the share inside $15–$100

**Avg price**

**Great****$47.80**

avg listing price — sweet spot $15–$100

**Returns**

**Great****1.6%**

return rate — above 5% kills the launch gate

**Growth**

**Good****+39.8%**

90-day search growth — must beat 0% to launch

**Market size**

**Good****$302K**

$302K/yr · 42K searches

**Review moat**

**Okay****2,015.47**

avg incumbent reviews — the moat a new listing must climb

**Competition**

**Bad****70%**

top-5 click share — a locked-up shelf

**Quality gap**

**Bad****4.7★**

avg incumbent rating — lower means beatable quality

**Brand share**

**Bad****94%**

top-5 brand share — brand-locked demand

## Reviews