21mm flange insert
Skip itPrices mostly outside the sweet spot ($6.92–$14.62) — this niche doesn't clear our bar today.
Conversion
Incredible14.6%search→purchase rate — share of searches ending in a sale
Review moat
Okay1,579.86avg incumbent reviews — the moat a new listing must climb
Quality gap
Okay4.5★avg incumbent rating — lower means beatable quality
Returns
Okay4.8%return rate — above 5% kills the launch gate
Avg price
Okay$9.27avg listing price — sweet spot $15–$100
Growth
Bad-7.5%90-day search growth — must beat 0% to launch
Brand share
Bad93%top-5 brand share — brand-locked demand
Market size
Bad$53K$53K/yr · 40K searches
Competition
Bad93%top-5 click share — a locked-up shelf
Price range
Bad$6.92–$14.62cheapest 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
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.No pronounced peak months · busiest ÷ quietest = 1.4×
Top 21mm flange insert search terms
- 21mm flange insert22K/yr
- 21 mm flange insert14K/yr
- 21 flange inserts3K/yr
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.
All 7 tracked products in this niche — three views at once, no toggling.
Top sellers
by 90-day click share
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$7.974.5★971 rev
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$9.884.5★562 rev
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$7.844.5★635 rev
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$7.964.6★347 rev
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$14.624.5★3,517 rev
Newest
by launch date4Pcs 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$7.84635 rev
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$6.92848 rev
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$7.97971 rev
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$9.684,179 rev
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$9.88562 rev
Trending
90-day click momentumFlange 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$7.964.6★
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$7.844.5★
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$9.684.6★
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$9.884.5★
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$7.974.5★
What buyers say about 21mm flange insert
What buyers praise and complain about, mined from review topics.What buyers love
“The best sizing kit”
“One thing that really stood out to me was how well-made”
“Great price”
“are very comfy”
“The little cleaning sponge is wonderful”
“Easy to use”
“It performs exactly as intended”
“Very helpful and useful for breastfeeding”
“durable”
“Compatible with spectra pumps”
What buyers complain about
“Not true size”
“Poor quality”
“one of the flange inserts tore right apart immediately after opening”
“Waste of money”
“Not comfortable”
“Burned my skin”
“It makes the arduous”
“the material is not as soft”
“Material hurts”
“Too sticky; nipple can move”
Top return reasons
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.