M4 x 0.7mm x 1.5D Helicoil Wire Inner Thread Inserts, Coiled Wire Helical Screws, 304 Stainless Steel, Metric, 100Pcs

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.

We use these for our laser cut acrylic projects for when we need screws in to the plastic. These always work

Worked well. Held tight.

One day shipping, a good price and they worked just fine.

Order 2 sizes. Good Helicoil Wire Inner Thread Inserts

Great product, just shorter than advertised.

Worked as they should, but how often are you going to need 150.

Ok