Trimmers & Edgers
String trimmer line: gauge, shape and feed explained
The line is the only part of a trimmer that touches the grass, and it is the spec people skip.
Affiliate disclosure: we earn a commission if you buy through our links, at no extra cost to you. It never changes which product we rank first — here is how we're funded.
We have not tested these units. Every spec on this page comes from the manufacturer's own documentation and is linked to it. Every computed figure is arithmetic you can redo. Prices are checked daily — last verified January 1, 1970. Here is exactly how we pick.
A string trimmer is a motor, a shaft and a piece of plastic filament doing all the work. Every spec that matters is about that filament: how thick it is, what shape it is, and how much of a nuisance it is to replace. Two of those three are published, and the third decides whether the tool stays in the shed.
Gauge: the one spec to get right
| Trimmer | Specified line | Swath | Feed | What it suits |
|---|---|---|---|---|
| EGO ST1521S | 0.095 in dual-feed spiral twist | 15 in | POWERLOAD automatic winding | Mixed lawn edge and heavy growth |
| Ryobi RY402110 | 0.095 in | Adjustable 15-17 in | Bump feed | Long sessions, variable width |
| Greenworks ST80L210 | 0.080 in spiral twist dual-line | 16 in | Bump feed | Lawn edges and light weeds |
Line gauges and swaths as published by each manufacturer on the product pages cited below. Feed type is the manufacturer's own description of the head.
Greenworks is unusually candid about what its lighter line means: the 0.080 in gauge is a lawn-edge line, and it will break more often in heavy weeds. That is not a flaw, it is a design point — thinner line spins with less drag, which is part of how that tool gets 45 published minutes from a 160Wh pack. Buying the 80V Greenworks and then attacking brambles with it is using the wrong tool.
The 0.095 in gauge on the EGO ST1521S and the Ryobi RY402110 is the heavier of the two common home gauges. If your trimming includes fence lines, tree bases and the rough ground behind the shed, that is the one to be on.
Shape: what spiral twist is actually claiming
Both EGO and Greenworks specify spiral twist line. A twisted profile presents a continuously changing edge to the grass rather than a flat round face, and it is marketed as quieter and cleaner-cutting than plain round line.
Dual-line and dual-feed heads — two strands rather than one — are specified on the EGO and the Greenworks. Two cutting edges per revolution is a straightforward advantage in dense growth and a straightforward disadvantage in line consumption. Neither is quantified anywhere we can cite.
Feed: the spec that decides whether you use the tool
Reloading a trimmer head is the job everyone hates: unclip the spool, find the line, feed it through two eyelets, wind it under tension, clip it back. Doing that in a hedge bottom on a hot afternoon is why trimmers end up in the back of sheds.
- Automatic reload (EGO POWERLOAD). You feed the line through and the head winds it for you. It is the single most useful feature on any trimmer in this comparison, and it is the reason the EGO stays at the top of our trimmer roundup.
- Bump feed. Tap the head on the ground and a length of line advances. Reliable, universal, and it does nothing for the moment the spool runs out.
#ad Check the EGO ST1521S POWERLOAD price on Amazon — how we're funded.
Swath, and what it costs in energy
A wider swath finishes an open verge faster and is harder to control against a fence. Ryobi is the only trimmer here that lets you choose, publishing an adjustable 15 to 17 inch swath — wide for the long boundary, narrow for the flower bed. It is also the heaviest at a published 12.9 lb with the 6.0Ah pack fitted, which is the trade.
#ad Check the Ryobi RY402110 price on Amazon — how we're funded.
When line is the wrong tool entirely
Line cuts grass. It does not cut a clean vertical edge along a path, and using it that way is how you end up with a scalloped border and a lot of soil on the driveway. For that job the tool is a blade: EGO's EA0800 edger attachment publishes an 8 in blade and up to 3 in of adjustable depth, on the same power head as the trimmer.
The full method — where to cut, how deep, and how much edge you get per charge — is on the edging guide, and the tools themselves are compared on the edger page.
Line is consumable. The platform is not.
Line is the cheapest thing you will buy for the tool, and the pack is one of the most expensive. A trimmer bought on a platform you already own is a trimmer that costs you a head and some filament; a trimmer bought off-platform is a battery purchase wearing a trimmer costume.
The Greenworks ST80L210 is the lightest published trimmer here at 7.1 lb bare, with a 30-minute recharge and a 4-year battery warranty — a good tool and an expensive way to enter the 80V platform on its own. Check it on Amazon if you are already on 80V, and read the compatibility page if you are not.
What we cannot tell you
- How fast each head consumes line. Not published by anyone.
- Whether spiral twist is measurably quieter. No manufacturer publishes a figure for line noise.
- Which line brand lasts longest. That needs testing, and we test nothing.
- Trimming pace. The 1 MPH figure in the arithmetic above is our stated assumption so the maths is checkable, not a measurement.
The products discussed
Specs are the manufacturer's own and linked to the page they came from. Prices come from a live daily check; where we have no verified price we say so rather than print a stale one.
EGO Power+ 15" POWERLOAD Carbon Fiber ST1521S
EGO · EGO 56V ARC Lithium · Our score 8.9/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
A lifetime shaft warranty and a head that reloads line at the push of a button -- the two things that actually go wrong with a string trimmer.
Published specs
| Cutting swath | 15 in |
|---|---|
| Line | 0.095 in dual-feed spiral twist |
| Head | POWERLOAD automatic winding |
| Shaft | Carbon fiber, split shaft |
| Battery (kit) | 56V 2.5Ah |
| Runtime claim | Up to 30 min on 2.5Ah |
| Charge time | 50 min |
| Warranty | 5-yr tool / 3-yr battery, lifetime shaft |
Source: POWER+ 15" POWERLOAD String Trimmer with Carbon Fiber Shaft, egopowerplus.com
56V x 2.5Ah = 140Wh. 30 minutes of published runtime from 140Wh is about 4.7Wh per minute -- roughly a quarter of what a blower on turbo burns.
What the numbers favor
- Lifetime warranty on the carbon fiber shaft, published
- POWERLOAD winds the line for you -- the job everyone hates
- 0.095 in line, the heavier of the two common home gauges
- Split shaft, so it takes EGO's multi-head attachments
What they don't
- Ships with the small 2.5Ah pack; 30 minutes is a modest published runtime
- EGO does not publish a weight for this configuration
you only edge a short driveway. An 8 in edger attachment on a power head you already own does that job better and costs a fraction.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Ryobi 40V HP Whisper 17" Carbon Fiber RY402110
Ryobi · Ryobi 40V · Our score 8.6/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
67 published minutes and a swath you can dial from 15 to 17 inches -- the only adjustable-swath trimmer here.
Published specs
| Cutting swath | Adjustable 15-17 in |
|---|---|
| Line | 0.095 in bump feed |
| Shaft | Carbon fiber |
| Battery (kit) | 40V 6.0Ah |
| Runtime claim | Up to 67 min |
| Weight | 8.8 lb bare / 12.9 lb with 6.0Ah |
| Length | 72.25 in |
Source: 40V HP Brushless 17" String Trimmer (RY402110), ryobitools.com
40V x 6.0Ah = 240Wh. 67 minutes from 240Wh is about 3.6Wh per minute -- the most efficient published figure of the three trimmers here.
What the numbers favor
- 67 minutes published, more than double the EGO kit's 30
- Swath adjusts 15-17 in, so tight borders and open verge get the same tool
- Best published watt-hours per minute of the trimmers on this page
- Whisper Series noise engineering, same line as the 57 dB blower
What they don't
- 12.9 lb with the 6.0Ah pack fitted -- the heaviest trimmer here, and it is held at arm's length
- Ryobi publishes no noise figure for this specific model
- Bump feed, not an automatic reload head
you have wrist or shoulder trouble. 12.9 lb on the end of a 72 in shaft is a lot of leverage, whatever the runtime says.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Greenworks 80V 16" String Trimmer ST80L210
Greenworks · Greenworks 80V · Our score 8.4/10
#ad No verified live price right now, so we show none rather than a stale one. How we're funded.
7.1 lb bare with a 30-minute recharge and a 4-year battery warranty -- the lightest way onto the 80V platform.
Published specs
| Cutting swath | 16 in |
|---|---|
| Motor | Brushless, 6200 RPM |
| Line | 0.080 in spiral twist dual-line bump feed |
| Battery (kit) | 80V 2.0Ah |
| Runtime claim | Up to 45 min |
| Recharge | 30 min |
| Weight | 7.1 lb without battery |
| Warranty | 3-yr tool / 4-yr battery |
Source: 80V Cordless 16" Brushless String Trimmer (ST80L210), greenworkstools.com
80V x 2.0Ah = 160Wh. 45 minutes from 160Wh is about 3.6Wh per minute, matching the Ryobi almost exactly despite half the pack size.
What the numbers favor
- 7.1 lb bare, the lightest published trimmer weight here
- 30-minute recharge, the fastest on this page
- 4-year battery warranty
- Publishes motor RPM, which neither EGO nor Ryobi does for their trimmers
What they don't
- 0.080 in line is the lightest gauge here -- it will break more often in heavy weeds
- 160Wh included is a small pack for an 80V platform
- Bump feed, not automatic reload
you cut heavy brush or thick weed stems. 0.080 in line is a lawn-edge gauge, not a bramble gauge.
How it scores
Scores are our editorial weighting of the published specs above, not a test result. They are deliberately kept out of this page's structured data.
Where to buy the tools on this page
Every link below is an Amazon affiliate link. We show no price we have not verified today, so where there is no live figure the link says "check price" and takes you to the listing to read it there.
Best overall
EGO Power+ 15" POWERLOAD Carbon Fiber ST1521S
EGO · EGO 56V ARC Lithium
Best runtime
Ryobi 40V HP Whisper 17" Carbon Fiber RY402110
Ryobi · Ryobi 40V
Best light 80V option
Greenworks 80V 16" String Trimmer ST80L210
Greenworks · Greenworks 80V
#ad As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. How we're funded.
Common questions
What size trimmer line should I use?
Is 0.095 line better than 0.080?
Can I put thicker line in my trimmer?
What does spiral twist line do?
What is the difference between bump feed and automatic reload?
How much line does a job use?
Sources
- EGO POWER+ 15" POWERLOAD String Trimmer with Carbon Fiber Shaft, egopowerplus.com
- RYOBI 40V HP Brushless 17" String Trimmer (RY402110), ryobitools.com
- Greenworks 80V Cordless 16" Brushless String Trimmer (ST80L210), greenworkstools.com
- EGO POWER+ 8" Edger Attachment (EA0800) Multi-Head System, egopowerplus.com
Read next
- Trimmers & Edgers
The line gauge and the head design decide whether you enjoy this job or dread it.
- Best cordless string trimmers of 2026
Three trimmers ranked on swath, line gauge, weight and energy per minute.
- String trimmer buying guide: the four specs that matter
Line gauge, head type, shaft and loaded weight -- the four specs that decide how a trimmer feels.
- How to edge a lawn properly
Depth, sequence and the feet-of-edge-per-charge arithmetic from four published pack sizes.
- Best cordless lawn edger
The attachment usually beats the dedicated machine here. Published runtimes and the depth spec that matters.
- Are EGO batteries interchangeable? And will they work with Ryobi?
Which packs fit which tools, stated plainly, plus the one place brands quietly break their own rule.