---
title: "21mm Flange Insert — $53K/yr Amazon US Niche (2026) - Flapen"
canonical_url: "https://flapen.com/research/us/baby-products/21mm-flange-insert"
last_updated: "2026-08-09T02:47:08.071Z"
locale: en
meta:
description: "Niche score 28/100 · $53K/yr market · 40K searches/yr · $9.27 avg price. Doesn't clear our bar today. Data updated Jul 2026."
"og:description": "Niche score 28/100 · $53K/yr market · 40K searches/yr · $9.27 avg price. Doesn't clear our bar today. Data updated Jul 2026."
"og:title": "21mm Flange Insert — $53K/yr Amazon US Niche (2026) - Flapen"
---
# **21mm flange insert**
**Skip it**
Prices mostly outside the sweet spot ($6.92–$14.62) — this niche doesn't clear our bar today.
Market size 13Growth 21Conversion 97Competition 6Returns 28Price range 0Avg price 27Brand share 19Review moat 49Quality gap 37
**Conversion**
**Incredible****14.6%**
search→purchase rate — share of searches ending in a sale
**Review moat**
**Okay****1,579.86**
avg incumbent reviews — the moat a new listing must climb
**Quality gap**
**Okay****4.5★**
avg incumbent rating — lower means beatable quality
**Returns**
**Okay****4.8%**
return rate — above 5% kills the launch gate
**Avg price**
**Okay****$9.27**
avg listing price — sweet spot $15–$100
**Growth**
**Bad****-7.5%**
90-day search growth — must beat 0% to launch
**Brand share**
**Bad****93%**
top-5 brand share — brand-locked demand
**Market size**
**Bad****$53K**
$53K/yr · 40K searches
**Competition**
**Bad****93%**
top-5 click share — a locked-up shelf
**Price range**
**Bad****$6.92–$14.62**
cheapest to priciest tracked listing — scored on the share inside $15–$100
According to Flapen's Amazon United States niche tracking, 21mm flange insert is a $53K/yr Amazon United States market (40K searches/yr). The top 5 brands hold 93% of demand. Verdict: Skip it — 28/100.
Data updated Jul 12, 2026 · scored weekly · [~~How we score niches ~~](https://flapen.com/research/methodology)
## **21mm flange insert market data**
- **Units sold / yr**
- **6K–8K**
- avg 500–750/product
- **Revenue / yr**
- **$56K–$74K**
- units × avg price
- **Conversion rate**
- **14.6%**
- **Avg BSR**
- **#36**
- **Page quality**
- **0%**
- **Prime**
- **100%**
- **Sponsored**
- **100%**
- **Out of stock**
- **6.8%**
- **Avg brand age**
- **37 months**
- **Avg seller age**
- **140 days**
## **Competition & brand share**
The top 5 products capture 93% of clicks — a locked-up shelf that new listings rarely crack.
**Brands**
**7 **▼falling
**Sellers**
**9**
**Top-5 brand share**
**93%**
Top 20: 100%
**Top-5 click share**
**93%**
Top 20: 100%
**Open market**
**3%**
- Suniceme53% - Hranio24% - BDICOVE6% - GOCROWEEN6% - Maymom4% - Nuliie4% - Open — no brand owns it (1 brand, 3%)
## **Demand & seasonality**
Weekly Amazon search volume, last 104 weeks — -7.5% search growth over the last 90 days.
1K600Spike '25Spike '26 seasonSepDecMarJunAugNovMarMay
No pronounced peak months · busiest ÷ quietest = 1.4×
[**Open Trend **](https://flapen.com/research/us/baby-products/21mm-flange-insert/trend)
## **Top 21mm flange insert search terms**
- **21mm flange insert**22K/yr-8.5%14.1% conv. - **21 mm flange insert**14K/yr-6.6%13.5% conv. - **21 flange inserts**3K/yr-5.8%12.2% conv. [**All search terms **](https://flapen.com/research/us/baby-products/21mm-flange-insert/search-terms)
## **Top 21mm flange insert products on Amazon**
Each bubble is one product — market share against review moat; bubble size tracks estimated sales, color grades how beatable the incumbent looks.
0%15%$8K30%$16K45%$24K60%$32K1001K10K Reviews — right = deep review moatMarket share (90d) ≈ est. sales
Beatable (≤4.3★) Contested Strong incumbent (>4.7★)
All 7 tracked products in this niche — three views at once, no toggling.
### **Top sellers**
by 90-day click share
[1**Flange Inserts 21mm Compatible with Medela/Spectra/TSRETE/Elvie/Momcozy/Bellababy Breast Pump 24mm Shields/Flanges Reduce 24mm Nipple Tunnel Down to 21 mm 4PCS**Suniceme**$7.97**4.5★971 rev](https://www.amazon.com/dp/B0CW1VDP9D) [2**21mm Flange Insert 6PC Compatible with 21mm Flange Spectra/Flange Inserts for Spectra Flange 21mm/Momcozy Wearable Breast Pump Flange Insert/Medela Flange 21mm/Elvie/Willow/TSRETE**Hranio**$9.88**4.5★562 rev](https://www.amazon.com/dp/B0CL5MM4HH) [3**4Pcs Breast Pump Flange Insert 21mm Compatible with Momcozy/Spectra/Medela/eufy/Elvie/Lansinoh/Paruu P10 Breast Pump Fit for Momcozy M5/M9/M6/V2 Pro/V2 pro/S12 Pro/eufy E10 S1 S1 Pro 24mm Flange**BDICOVE**$7.84**4.5★635 rev](https://www.amazon.com/dp/B0DS6YQGNT) [4**Flange Inserts 21mm 8PC Compatible with Momcozy S12 pro/S9 pro/S9/S10/S12/Medela/TSRETE/Spectra/Bellababy etc 24mm Wearable Breast Pump Reduce 24mm Tunnel Down to Correct Size**GOCROWEEN**$7.96**4.6★347 rev](https://www.amazon.com/dp/B0CM5RB96P) [5**Maymom Flange 21mm Insert Compatible with Medela/Spectra/Elvie/momcozy/tsrete/Willow/Motif Luna/Ameda MYA Breastpump 24mm Breast Shields. Reduce 24mm Niple Tunnel Down to 21mm**Maymom**$14.62**4.5★3,517 rev](https://www.amazon.com/dp/B0BGXPQ6VS)
**~~View all top sellers →~~**
### **Newest**
by launch date
[**4Pcs Breast Pump Flange Insert 21mm Compatible with Momcozy/Spectra/Medela/eufy/Elvie/Lansinoh/Paruu P10 Breast Pump Fit for Momcozy M5/M9/M6/V2 Pro/V2 pro/S12 Pro/eufy E10 S1 S1 Pro 24mm Flange**BDICOVE**$7.84**635 rev1y ago](https://www.amazon.com/dp/B0DS6YQGNT) [**IVARONAL Flange Insert 2PCS 21mm Compatible with Momcozy M9/M6/M5/S12 Pro/V1 Pro/V2 pro Spectra/Medela/Elvie/NCVI/TSRETE/eufy/Lansinoh/Paruu/MomMed Breast Pump 24mm Shields/Flanges (2pcs-21mm)**IVARONAL**$6.92**848 rev2y ago](https://www.amazon.com/dp/B0D4DMXGJ1) [**Flange Inserts 21mm Compatible with Medela/Spectra/TSRETE/Elvie/Momcozy/Bellababy Breast Pump 24mm Shields/Flanges Reduce 24mm Nipple Tunnel Down to 21 mm 4PCS**Suniceme**$7.97**971 rev2y ago](https://www.amazon.com/dp/B0CW1VDP9D) [**Nuliie 3-in-1 Flange Sizing Kit 13/15/17/19/21mm for 24mm Electric Double Breast Pump Flange/Shield 10PCS Silicone Flange Inserts to Boost Pumping Efficiency & Comfort BPA-Free Essential for Moms**Nuliie**$9.68**4,179 rev2y ago](https://www.amazon.com/dp/B0CMPBBHMZ) [**21mm Flange Insert 6PC Compatible with 21mm Flange Spectra/Flange Inserts for Spectra Flange 21mm/Momcozy Wearable Breast Pump Flange Insert/Medela Flange 21mm/Elvie/Willow/TSRETE**Hranio**$9.88**562 rev2y ago](https://www.amazon.com/dp/B0CL5MM4HH)
**~~View all new products →~~**
### **Trending**
90-day click momentum
[**Flange Inserts 21mm 8PC Compatible with Momcozy S12 pro/S9 pro/S9/S10/S12/Medela/TSRETE/Spectra/Bellababy etc 24mm Wearable Breast Pump Reduce 24mm Tunnel Down to Correct Size**GOCROWEEN**$7.96**4.6★**▲ 143%**](https://www.amazon.com/dp/B0CM5RB96P) [**4Pcs Breast Pump Flange Insert 21mm Compatible with Momcozy/Spectra/Medela/eufy/Elvie/Lansinoh/Paruu P10 Breast Pump Fit for Momcozy M5/M9/M6/V2 Pro/V2 pro/S12 Pro/eufy E10 S1 S1 Pro 24mm Flange**BDICOVE**$7.84**4.5★**▲ 88%**](https://www.amazon.com/dp/B0DS6YQGNT) [**Nuliie 3-in-1 Flange Sizing Kit 13/15/17/19/21mm for 24mm Electric Double Breast Pump Flange/Shield 10PCS Silicone Flange Inserts to Boost Pumping Efficiency & Comfort BPA-Free Essential for Moms**Nuliie**$9.68**4.6★**▲ 18%**](https://www.amazon.com/dp/B0CMPBBHMZ) [**21mm Flange Insert 6PC Compatible with 21mm Flange Spectra/Flange Inserts for Spectra Flange 21mm/Momcozy Wearable Breast Pump Flange Insert/Medela Flange 21mm/Elvie/Willow/TSRETE**Hranio**$9.88**4.5★**— 4%**](https://www.amazon.com/dp/B0CL5MM4HH) [**Flange Inserts 21mm Compatible with Medela/Spectra/TSRETE/Elvie/Momcozy/Bellababy Breast Pump 24mm Shields/Flanges Reduce 24mm Nipple Tunnel Down to 21 mm 4PCS**Suniceme**$7.97**4.5★**— 6%**](https://www.amazon.com/dp/B0CW1VDP9D)
**~~View all trending →~~**
## **What buyers say about 21mm flange insert**
What buyers praise and complain about, mined from review topics.
### **What buyers love **
**Size-Overall**26%
*“The best sizing kit”*
**Quality-Overall**17%
*“One thing that really stood out to me was how well-made”*
**Value For Money**9%
*“Great price”*
**Comfort-Overall**7%
*“are very comfy”*
**Ease Of Cleaning**7%
*“The little cleaning sponge is wonderful”*
**Ease Of Use**6%
*“Easy to use”*
**Advertised Vs Actual Product**5%
*“It performs exactly as intended”*
**Breastfeeding Friendly**4%
*“Very helpful and useful for breastfeeding”*
**Durability**3%
*“durable”*
**Compatibility-Overall**2%
*“Compatible with spectra pumps”*
### **What buyers complain about **
**Size-Overall**25%
*“Not true size”*
**Quality-Overall**8%
*“Poor quality”*
**Durability**5%
*“one of the flange inserts tore right apart immediately after opening”*
**Value For Money**5%
*“Waste of money”*
**Comfort-Overall**5%
*“Not comfortable”*
**Skin Health**5%
*“Burned my skin”*
**Ease Of Use**4%
*“It makes the arduous”*
**Hard Feel**4%
*“the material is not as soft”*
**Material Quality**4%
*“Material hurts”*
**Adhesion/Stickiness**3%
*“Too sticky; nipple can move”*
### **Top return reasons **
**Size-Overall**61%
**Functionality-Overall**7%
**Advertised Vs Actual Product**6%
**Material Quality**4%
**Defective Material/Parts**4%
**Value For Money**3%
**Breastfeeding Friendly**2%
**Comfort-Overall**2%
**Width**2%
**Compatibility-Overall**2%
## **Common questions**
- **Is 21mm flange insert profitable to sell on Amazon United States?**
- The niche generates $53K/yr across 7 tracked products. 90-day search growth is -7.5%. Flapen's verdict: Skip it (28/100).
- **How competitive is the 21mm flange insert niche?**
- 7 brands and 9 sellers compete. The top 5 products take 93% of clicks and top 5 brands hold 93% of demand.
- **What do buyers complain about in 21mm flange insert?**
- Top complaints mined from reviews: Size-Overall, Quality-Overall, Durability. The return rate is 4.8%.
- **When does demand for 21mm flange insert peak?**
- Demand is steady year-round — the busiest month runs 1.4× the quietest.
- **What does it cost to enter the 21mm flange insert niche?**
- Listings span $6.92–$14.62; the average listing price is $9.27 (sweet spot $15–$100). The average incumbent carries 1,580 reviews — the moat a new listing must climb.
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