What Is Weed Eater Line Made Of and Does It Matter?
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What is weed eater line made of? Most often it is nylon, a tough plastic filament that spins fast enough to cut grass and light weeds. The material is only part of the picture. The line’s cross-section, its diameter and the way the head feeds new line all change how well it cuts and how often you stop to refill it. This guide explains what the common line types are made of, what the shape and size mean in practice, and what the product listings in our data pack say about their spools.
Quick answer
- Most trimmer line is nylon monofilament, which is a single strand of plastic rather than a twisted or braided cord.
- A round nylon line cuts grass and light woody growth well, according to the general reference on string trimmers.
- Some lines for more powerful cutters are extruded into a star-like shape, which the reference says helps the line cut through tougher growth.
- Electric trimmers are usually limited to nylon line up to about 2.5 mm (0.098 inch) in diameter, because of their lower power output.
What the line is made of
A string trimmer line is a long strand of plastic that the head throws outward at high speed. The strand has to be flexible enough to wind onto a spool, tough enough to survive repeated hits on stone and wood, and light enough to spin without tearing itself apart. Nylon meets those needs better than most plastics, which is why it is the common choice across brands.
The reference used for this guide describes nylon as the common material for trimmer line. It does not describe copolymer or square profile lines, so this guide does not make claims about those forms beyond what the product listings say. Several spool listings in our data pack describe their line as nylon, and one describes a “high-grade copolymer nylon resin.” Read the listing and the packaging for the exact formula, because the listings do not all name the same grade.
The spool is a separate part. The KAKO listing describes an ABS plastic spool for its Ryobi-compatible line, and the WETOOLPLUS listing describes a spool and cap for Worx models. The spool holds the line, and the line feeds through a small eyelet in the head. The spool and the line must match the head, which is why compatibility is the first thing to check.
Why the shape of the line matters
Most common lines are round in cross-section. A round line is simple to make, quiet in use and gentle on the motor. It cuts grass cleanly and handles light woody stems. Round line is the default choice for most homeowners, and it suits the edging work that many cordless trimmers are sold for.
Some lines use a different profile. The reference describes monofilament lines for more powerful cutters that are extruded in a star-like shape. The idea is that the extra edges cut more aggressively, which helps with thicker or tougher growth. The reference does not say how much more aggressive a star profile is, so treat it as a design choice, not a measured benefit. A star or shaped line is most useful on a stronger trimmer, and it can be harder on a small electric motor.
The shape also changes how the line wears. A line that is worn down to a smaller effective diameter cuts less well, and a line that breaks at the eyelet stops the head from feeding new line. Check the line as you work, and replace it when it is short or frayed.
Why diameter matters more than most buyers expect
Line diameter sets the load on the motor and the strength of the cut. The reference describes gasoline trimmers with engines of at least 21 cc, which can turn 2 mm line easily, and a 32 cc engine that can swing about 2.75 mm line. Electric trimmers are usually limited to nylon line with a maximum diameter of 2.5 mm (0.098 inch), because their power output is lower.
The spool listings in our pack show how wide the range is in practice. The KAKO spool for Ryobi-compatible trimmers lists a 0.065-inch line. The WETOOLPLUS spool for Worx-compatible trimmers lists a cutting width of 0.08 inches in its specs. The MtiolHig trimmer in the same pack comes with 18 extra 0.11-inch lines, which is thicker than either spool. Use a line that is no thicker than the trimmer’s rated size. Going thicker than the trimmer is built for can overload the motor and cause the head to stall.
When you buy replacement line, match the diameter the trimmer’s manual or head label gives. A thinner line feeds more easily but wears faster, and a thicker line is stronger but takes more power to spin. The best match is the diameter the manufacturer lists.
How the line feeds: bump, auto, and fixed-line
The feed type decides how you get new line when the old one wears out. The reference describes three main systems.
- Bump feed: The reel holds wound line. Tapping the head on the ground releases a little more line as the old line wears or breaks.
- Auto feed: A newer bump-feed design includes a small cutter that trims the exposed line to a length that can be swung effectively. The Elegarden and KAKO listings in our pack describe an automatic feed system.
- Fixed-line: The head takes pre-cut line inserts that are threaded into slots. The reference says this makes feeding and troubleshooting easier than with a bump-feed head.
The Elegarden listing describes an auto line feed system that keeps the line at a working length. The KAKO listing describes pre-wound spools for an auto-feed head, which saves winding the line by hand. Auto feed heads are common on cordless trimmers, but they still need the right spool. A spool that is the wrong size will not seat properly and will not feed.
Products from our data pack
The four products below come from the product data pack for this topic. Each section states only what its listing says.
MtiolHig 3-in-1 cordless trimmer with 18 extra lines
This trimmer is a battery-powered 3-in-1 tool that the listing says works as a trimmer, edger and mower. The listing says it comes with 18 extra 0.11-inch thick lines, and it gives an 11-inch cutting width and a speed of 4800 RPM in its specs. The bullets describe an adjustable guard that protects flowers and shrubs. The listing states that the battery and charger are not included. The 0.11-inch line is thicker than the spool products in this pack, so check that the trimmer head is rated for that diameter before you buy line.
KAKO replacement spool for Ryobi One+ trimmers
This product is a set of 12 spools and two caps, listed as compatible with Ryobi One+ AC14RL3A spools. The listing gives a line diameter of 0.065 inch and a line length of 11 feet per spool. It describes the line as nylon and the spool as ABS plastic. The listing lists a range of compatible Ryobi model numbers for 18V, and a 24V model number, so match your model number against the list before ordering. This is the most common choice for a Ryobi trimmer owner who wants a large supply of pre-wound line.
WETOOLPLUS spool and cap for Worx trimmers
This product is a 3-spool and 1-cap kit listed as compatible with Worx models WG168, WG184, WG190 and WG191. The listing says the spool is made of a high-grade copolymer nylon resin, and the specs give a cutting width of 0.08 inches. The listing describes an anti-tangle, no-jam design and a cap that secures the spool. It is a direct replacement for the Worx part WA0014 according to the listing. The kit is a practical choice if your trimmer is one of the listed Worx models.
Elegarden cordless trimmer with auto line feed
This Elegarden model is a 12-inch cordless trimmer with an automatic line feed system. The listing says the system keeps the line at a working length while you cut, which reduces stops for line adjustments. It is sold as a bare tool, and the listing says the battery and charger are not included. The listing gives 8500 RPM and a 12-inch cutting width. If you choose this trimmer, buy line that the Elegarden manual or head label lists, and check the head’s rated diameter.
How to choose line
Start with the trimmer. The manual or head label gives the rated diameter and the spool type. Next, decide the feed type. A bump-feed head takes wound line, a fixed-line head takes pre-cut inserts, and an auto-feed head takes a pre-wound spool. Then choose the material. Nylon is the default. A round line suits grass and edges, and a star-shaped line is for tougher work on a stronger trimmer.
Avoid buying line by diameter alone. A 0.065-inch line may fit one head and not another, even if both trimmers are described as 18V. Check the model number, the head type and the rated diameter before you buy.
Common mistakes with trimmer line
- Using line thicker than the trimmer is rated for. A line that is too thick can overload the motor and stall the head.
- Assuming every spool fits every head. Check the model list in the listing before you buy.
- Running line down to a stub. Short line cuts poorly and can break at the eyelet.
- Mixing line types in one head. Use the type and diameter the head is built for.
- Cutting near electrical lines or fences without a plan. Keep the line clear of wires and ask an electrician if a job is close to a power line.
FAQ
Is weed eater line the same as fishing line?
No. Trimmer line is designed to spin at high speed and resist abrasion from grass and stone. Fishing line is designed for a different job. Use the line that the trimmer manufacturer lists for your head.
Why is my line breaking so fast?
A line that is too thin for the work, or one that is worn down, breaks faster. Line that hits stone or wood also wears quickly. Use the diameter the trimmer is rated for, and replace the line when it is short.
Can I use a thicker line for stronger cutting?
Only up to the trimmer’s rated diameter. The reference says electric trimmers are usually limited to nylon line of about 2.5 mm (0.098 inch) maximum. A line that is thicker than that can overload the motor.
What is the difference between round and star line?
A round line is simple, quiet and gentle on the motor. A star-shaped line is extruded with extra edges for cutting tougher growth, and it is generally used on more powerful cutters. The reference does not measure the difference, so choose by your trimmer’s rating.
Does auto feed mean I never need to refill?
No. Auto feed gives you a new length of line when you tap the head, but the spool still runs out. Keep a spare spool or line on hand for longer jobs.
Bottom line
Weed eater line is usually nylon, and most trimmers use a round line. The shape, diameter and feed type decide how well the line cuts and how often you refill it. Match the line to your trimmer’s rated diameter and head type, use the spool listed for your model, and replace the line before it gets too short to cut well.
