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String Trimmer Line Types

A simple guide to the most common weed wacker string types

String trimmer line comes in a few common shapes, and the best choice depends on the kind of trimming you do most often. For most homeowners, round line is the most common and easiest option, while twisted, square, and serrated line are better for tougher cutting jobs.

What Trimmer Line Does

Trimmer line is the cutting cord that spins fast enough to slice grass and weeds along fences, sidewalks, flower beds, and driveways. The line shape affects how cleanly it cuts, how long it lasts, and how much noise or vibration the trimmer produces.

Most Common Line Types

Round line

Round line is the most common type of trimmer string. It is easy to load, widely available, and durable enough for regular yard trimming, which makes it a solid choice for general use.

Twisted line

Twisted line is shaped to give a cleaner cut and better performance on thicker grass. It is also often quieter than round line and can reduce vibration, which makes it a good middle-ground option.

Square or multi-sided line

Square and other multi-sided lines have sharper edges that cut more aggressively than round line. They work well on thick weeds and heavier growth, but they may wear faster if they hit hard surfaces often.

Serrated line

Serrated line has tooth-like edges that help it bite into dense weeds. It is a strong option for tougher trimming jobs where standard round line does not cut fast enough.

Which One To Use

  • Use round line for routine trimming around the home.

  • Use twisted line for a cleaner cut and less noise.

  • Use square or multi-sided line for thicker weeds and tougher vegetation.

  • Use serrated line for heavier overgrowth and stubborn weeds.

Line Size Matters Too

Line shape is only part of the choice. Thinner line is better for light trimming, while thicker line is better for dense weeds and rougher jobs. Matching the line size to your trimmer head and the work you do will help the tool perform better and reduce line breakage.

Best Starting Point

If you are not sure where to begin, round line is the safest everyday choice. If you trim thicker grass or weeds often, twisted or square line may give you better results.

Koenig Support Tip

If you are replacing trimmer line and want the easiest option, start with the line type your machine recommends, then move up to a more aggressive shape only if your trimming conditions call for it. That keeps the tool easier to use and helps you avoid buying line that is too heavy for your trimmer.