---
title: "Reviews — 21v バッテリー - Flapen"
canonical_url: "https://flapen.com/research/jp/diy/21v/reviews"
last_updated: "2026-08-08T06:02:22.565Z"
locale: en
meta:
  description: "Niche score 55/100 · ¥4.1M/yr market · 56K searches/yr. Pricing outside the sweet spot ($3288.25 avg) keeps it on the watch list. Data updated Jul 2026."
  "og:description": "Niche score 55/100 · ¥4.1M/yr market · 56K searches/yr. Pricing outside the sweet spot ($3288.25 avg) keeps it on the watch list. Data updated Jul 2026."
  "og:title": "Reviews — 21v バッテリー - Flapen"
---

# **21v バッテリー**

**Worth a look**

Shows a thin review moat (39 avg reviews), but pricing outside the sweet spot ($3288.25 avg) keeps it on the watch list.

Market size 97Growth 31Conversion 28Competition 53Returns 77Price range 0Avg price 0Brand share 31Review moat 98Quality gap 96

**Review moat**

**Incredible****38.8**

avg incumbent reviews — the moat a new listing must climb

**Market size**

**Incredible****¥4.1M**

¥4.1M/yr · 56K searches

**Quality gap**

**Incredible****3.9★**

avg incumbent rating — lower means beatable quality

**Returns**

**Great****1.9%**

return rate — above 5% kills the launch gate

**Competition**

**Good****53%**

top-5 click share — leaders hold, buyers still browse

**Growth**

**Okay****+4.7%**

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

**Brand share**

**Okay****87%**

top-5 brand share — brands hold most of the demand

**Conversion**

**Okay****2.2%**

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

**Avg price**

**Bad****¥3288.25**

avg listing price — sweet spot $15–$100

**Price range**

**Bad****¥1753.19–¥5500.13**

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

**Signals**[** Low Review Barrier**](https://flapen.com/research/niches?market=jp&signal=low_review_barrier "Top brand's reviews < 500") [** Quality Gap**](https://flapen.com/research/niches?market=jp&signal=quality_gap "Avg rating < 4.0") [** High Price**](https://flapen.com/research/niches?market=jp&signal=high_price "Avg price > $50")

## Reviews