String Trimmer Heads - Everything you Need To Know! Decoding Myths

Understanding Different String Trimmer Line Heads: A Guide for Landscapers

String trimmers are essential tools for commercial landscaping, helping professionals maintain edges and tackle tough vegetation. However, one challenging aspect of using string trimmers can be managing the line heads. Today, we delve into the various types of string trimmer line heads available, including bump heads, auto-feeding heads, and fixed-line heads, their maintenance, and how to select the best one for your needs.

Bump Heads: Reliable and User-Friendly

The bump head is a classic component found in many commercial string trimmers. For instance, the Stihl 25-2 head is popular in the US and comes standard on many Stihl trimmers. Renowned for its reliability, this head holds 33 feet of line, making it a favorite among commercial users. Its functionalities are straightforward:

  • Bump to Feed: Simply tap the head against the ground to release more line as needed.
  • Durability: Known for its long-lasting design.
  • Maintenance Tip: It’s crucial to use fresh line since old, brittle line tends to break easily and causes frustration.

To replace the line in a bump head:

  • Ensure the trimmer line is not too short; otherwise, it won’t feed properly.
  • Fresh, new line will prevent breakage and ensure smoother operation.

Fixed-Line Heads: Simplicity and Speed

Fixed-line heads appeal to those who value simplicity and quick line changes. Unlike bump heads, fixed-line heads use pre-cut line segments that you insert directly into the head:

  • Easy Installation: Insert pre-cut line segments into the head without the need for winding.
  • Quick Replacement: Ideal for quick changes, minimizing downtime.

A popular option in this category is one that accepts 7.25-inch line segments. These are easy to replace—simply pull out the worn line and insert a new segment through the designated slots.

Auto-Feeding Heads: Advanced Convenience

Advancements in trimmer technology have led to the development of auto-feeding heads, which automatically extend the line as it wears down:

  • Hassle-Free Operation: Eliminates the need for manual line feeding or bumping.
  • Efficiency: Keeps the line at an optimal length, improving the trimming performance.

The Stihl Autocut 26-2 is a contemporary example that closely resembles echo and Shindaiwa’s speed feed heads. With these heads, line installation is straightforward and doesn’t require disassembling the head. This feature is particularly beneficial for professionals seeking efficiency and ease of use.

Choosing the Right Line Thickness

It's essential to consider the line thickness, as it impacts both the efficiency of cutting and the load on the motor. Various heads support different line thicknesses:

  • Standard Trimmers: Typically accommodate line sizes from 0.08 inches to 0.105 inches.
  • Heavy-Duty Needs: For tougher jobs, such as roadside clearing, larger lines up to 0.155 inches might be necessary, requiring more powerful trimmers.

When selecting the line thickness, consider the trimmer's capacity to ensure it can handle the increased load without overheating or sustaining damage.


Choosing the right string trimmer head and line can greatly impact your landscaping efficiency and effectiveness. Whether you prefer the simplicity of a bump head, the quick line changes of a fixed-line head, or the advanced features of an auto-feeding system, there’s a solution that fits your landscaping needs. Always consider the type of vegetation, frequency of use, and trimmer compatibility when selecting your trimmer head. By understanding and utilizing the right tools, you can enhance your landscaping productivity and reduce downtime caused by maintenance issues. Remember, the key to optimal performance is also using fresh, appropriate-sized line suited to your specific trimmer head and the demands of the job.

Specifically, we discuss two myths in this video. (1) The amount of line that could fit in speed feed line heads, and (2) the maximum thickness of line that STIHL Duro Cut 20.2 accommodates.

Trimmer Line Heads discussed in the Video:


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