string line
Worth a lookShows searches that convert (12.9% search→purchase), but a failed launch gate (market size, growth, or returns) keeps it on the watch list.
Conversion
Incredible12.9%search→purchase rate — share of searches ending in a sale
Returns
Incredible0.8%return rate — above 5% kills the launch gate
Review moat
Good624.13avg incumbent reviews — the moat a new listing must climb
Price range
Good$5.97–$37.41cheapest to priciest tracked listing — scored on the share inside $15–$100
Avg price
Good$14.12avg listing price — sweet spot $15–$100
Market size
Good$395K$395K/yr · 217K searches
Brand share
Okay81%top-5 brand share — brands hold most of the demand
Growth
Okay+12.1%90-day search growth — must beat 0% to launch
Competition
Okay65%top-5 click share — leaders hold, buyers still browse
Quality gap
Okay4.6★avg incumbent rating — lower means beatable quality
According to Flapen's Amazon United States niche tracking, string line is a $395K/yr Amazon United States market (217K searches/yr). The top 5 brands hold 81% of demand. Demand peaks in Apr–May. Verdict: Worth a look — 56/100.
Data updated Jul 29, 2026 · scored weekly · How we score niches
string line market data
- Units sold / yr
- 25K–30K
- avg 1,000–1,250/product
- Revenue / yr
- $353K–$424K
- units × avg price
- Conversion rate
- 12.9%
- Avg BSR
- #20
- Page quality
- 0%
- Prime
- 100%
- Sponsored
- 88%
- Out of stock
- 4.0%
- Avg brand age
- 56 months
- Avg seller age
- 174 days
Competition & brand share
The top 5 products take 65% of clicks — established leaders, but buyers still shop beyond them.Brands
14 rising
Sellers
40
Top-5 brand share
81%
Top 20: 100%
Top-5 click share
65%
Top 20: 96%
Open market
13%
- ACE Supply23%
- GOLDEN COCK22%
- Romeda17%
- LURKA12%
- Generic7%
- BSRHOME6%
- Open — no brand owns it (8 brands, 13%)
Demand & seasonality
Weekly Amazon search volume, last 104 weeks — +12.1% search growth over the last 90 days.Peak months: Apr, May · busiest ÷ quietest = 2.7×
Top string line search terms
- string line71K/yr
- mason line32K/yr
- mason line string13K/yr
- construction string10K/yr
- mason string10K/yr
- stakes and string for yard marking6K/yr
- masonry line9K/yr
- mason string line7K/yr
- masonry string lines8K/yr
- construction string line9K/yr
Top string line 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 24 tracked products in this niche — three views at once, no toggling.
Top sellers
by 90-day click share
Mason Line String Reel 260FT 390FT 780FT 1500FT 2300FT Durable Construction Twine for Laying Bricks Blocks Fences in Gardening DIY & Landscaping Projects (Orange 262 Ft)
GOLDEN COCK$9.044.6★302 rev
Orange Mason Line String Line - #18 Braided Nylon String - 250 Ft Length - Nylon Twine for Gardening Or Masonry Tools - Perfect Construction String for A String Level Twine String for Gardening
ACE Supply$7.354.7★2,886 rev
Romeda Mason Line #18 500 Ft Orange String Construction Twine for Gardening & Masonry
Romeda$6.394.7★800 rev
LURKA Mason Line String #18 540 Feet Braided Construction Nylon Line with 5 Built-in Levels and Spool Fluorescent String Line for Precision Work DIY and Gardening (Fluorescent Orange)
LURKA$12.974.6★377 rev
Reloadable Line Reel Mason Line String Line 600 Ft Length Nylon Twine Nylon String for Gardening Or Masonry Tools Twine String for Gardening Yellow
BSRHOME$9.924.4★210 rev
Newest
by launch date
Konvixon 8PCS Mason String Line Set for Bricklaying Alignment & Masonry
Konvixon$37.4133 rev
Konvixon 10PCS Masonry Line String Set for Bricklaying and Alignment
Konvixon$28.7134 rev
Mason Line Cord with Handle Reloadable Reel #18 Braided Nylon Line 600 Feet of High Strength Nylon Line for Gardening or Masonry Tools Kite Twine Fluorescent Orange
Generic$9.9860 rev
Mason Line with Handle Reloadable Reel #18 Braided Nylon Line 600 Feet of High Strength Nylon Line for Gardening or Masonry Tools Kite Twine Fluorescent Yellow
Generic$9.9760 rev
KAOWQNL #18 Braided Mason Line String 580FT Nylon Twine with Handle Construction String Professional String Line Level Tool Kit with 6 Built in Levels & Storage Bag
KAOWQNL$12.9441 rev
Trending
90-day click momentumKonvixon 8PCS Mason String Line Set for Bricklaying Alignment & Masonry
Konvixon$37.414.5★
Konvixon 10PCS Masonry Line String Set for Bricklaying and Alignment
Konvixon$28.715.0★
Mason Line String 260FT 390FT 780FT 1500FT 2300FT Durable Construction Twine for Laying Bricks Blocks Fences in Gardening DIY & Landscaping Projects (Set 3 Colors 262 Ft x 3 Pcs)
GOLDEN COCK$8.174.6★
Mason Line Cord with Handle Reloadable Reel #18 Braided Nylon Line 600 Feet of High Strength Nylon Line for Gardening or Masonry Tools Kite Twine Fluorescent Orange
Generic$9.984.4★
Reloadable Line Reel Mason Line String line with Handle 600 Ft Length Nylon Twine 18 Braided Nylon String for Gardening Or Masonry Tools Outdoor KiteTwine String for Gardening Fluorescent Yellow
Generic$9.934.4★
What buyers say about string line
What buyers praise and complain about, mined from review topics.What buyers love
“It works as it should”
“Excellent quality”
“Strong and easy to work with”
“Easy to use and store”
“Worth the money”
“With its durable components and complete setup, it delivers strong functionality and very good value for the money”
“Bright color”
“Material is good plastic”
“Works well”
“The fluorescent yellow mason line is incredibly bright”
What buyers complain about
“not well made”
“Slightly thicker than some basic lines”
“i thought i was bigger than that on the picture”
“Expensive mistake for me”
“The hand reel broke within minutes”
“It had minimal stretching when used over several days”
“Now its unusable”
“The jig is not made of the thickest ABS-molded plastic material out there”
“It turned what could have been a fussy setup into a simple”
“Doesnt work as described”
Top return reasons
Common questions
- Is string line profitable to sell on Amazon United States?
- The niche generates $395K/yr across 24 tracked products. 1 of 2 products launched in the last 360 days are still selling. 90-day search growth is +12.1%. Flapen's verdict: Worth a look (56/100).
- How competitive is the string line niche?
- 14 brands and 40 sellers compete. The top 5 products take 65% of clicks and top 5 brands hold 81% of demand.
- What do buyers complain about in string line?
- Top complaints mined from reviews: Quality-Overall, Thickness, Size-Overall. The return rate is 0.8%.
- When does demand for string line peak?
- Demand peaks in Apr–May; the busiest month runs 2.7× the quietest.
- What does it cost to enter the string line niche?
- Listings span $5.97–$37.41; the average listing price is $14.12 (sweet spot $15–$100). The average incumbent carries 624 reviews — the moat a new listing must climb.