FAQ: What's this 'FRN' handle material?

"FRN" (fiberglass-reinforced nylon), sometimes called "GFN" (glass-filled nylon), is a high-strength plastic especially well-suited to the handles of folding knives.

Specifically, FRN is a nylon polymer mixed with glass fiber and then injection-molded into the desired shape. It's available in a variety of colors and textures.