M3 x 0.5mm x 1D Helicoil Wire Inner Thread Inserts, Coiled Wire Helical Screws, 304 Stainless Steel, Metric, 80Pcs

Worked as they should.

These worked very nicely to add machine thread holes to fiberglass on my boat. I was tired of repairing holes where wood screws directly into fiberglass stripped out or left stress cracks. This also works better than a wood screw in thicker fiberglass where wood screws tend to bind and snap off. The other benefit is that wood screw threads cutting into gelcoat tend to create stress points that start stress cracks in the gelcoat that radiate out from the screws. Using a helicoil with a machine thread screw seems to eliminate that problem. It is important to use an anticorrosion compound like Tef-Gel in the marine environment since, while these helicoils are stainless steel, they are not a marine-grade alloy.

The inserts expand in length when inserted. Fixed my problem.

Good product.

Used these M3×0.5 (1D) coils to fix stripped threads on an aluminum bracket and a 3D-printer part. The coils are consistent, no burrs, and standard M3 screws run in smooth with zero wobble. Tangs snapped cleanly with a punch. Once installed, the threads feel stronger than the originals. Tips: you’ll need the proper M3×0.5 STI tap and about a 3.2 mm drill. A dab of blue Loctite on the outside of the coil keeps it put. 1D length is perfect for shallow holes; if you need more engagement, look for 1.5D/2D.