THTEN KTHA 1040-03 Trimmer Head Compatible with Kobalt 40V KST 1040A-03,KST 1040B-03,KST 224A-03,KST 224B-03,KST 1540-06,KST 2540-06, KST 2580-06,KST 1341-06 String with 0.080 inch Pre Cut Line

What It Is

The THTEN KTHA 1040-03 is an aftermarket bump-feed trimmer head designed to replace the factory head on select Kobalt 40V string trimmers. It comes pre-loaded with 0.080-inch line, intended for light to medium trimming around edges, fences, and flower beds.

Fitment & Compatibility

This head is not universal—it only fits the specific Kobalt 40V models listed: KST 1040A-03, KST 1040B-03, KST 224A-03, KST 224B-03, KST 1540-06, KST 2540-06, KST 2580-06, and KST 1341-06. Before buying, confirm your model number (found on a label near the battery slot or lower shaft). The head uses 0.080-inch pre-cut line—do not use thicker line (e.g., 0.095-inch) as it may not feed or could damage the head. It is an aftermarket part, not OEM Kobalt, so fitment tolerances may vary slightly. Measure your shaft diameter (typically 1-inch) and check that the head’s internal thread matches your trimmer’s spindle (M10 x 1.25 left-hand thread is common for these models).

Key Things to Know

• Quality concerns: With a 2.6/5 rating from 25 reviews, common complaints include the head cracking after a few uses, line not feeding reliably, and the bump knob jamming. Expect shorter lifespan than OEM.
• Installation: Typically straightforward—remove old head by turning clockwise (left-hand thread), then screw on new head counterclockwise. No tools required, but ensure it’s snug to avoid wobbling.
• Line loading: Pre-loaded with 0.080-inch line, but reloading can be tricky. The head has a fixed line length (about 10-12 inches per side); trimming longer line may cause overfeeding or tangling.
• Gotcha: Some users report the head fits loosely on the spindle, causing vibration or uneven cutting. Check that the included washer/spacer matches your trimmer’s arbor.

Should You Buy It

Only buy this if you need an inexpensive, quick replacement for a dead OEM head on a listed Kobalt 40V model and are willing to accept lower durability and potential feeding issues. For frequent or heavy trimming, invest in the OEM Kobalt head (around $15-20) or a higher-rated aftermarket option like the Oregon 22-895.