Plastic eyeglasses frames as a rule tend to break more easily, especially kids' plastic eyeglass frames. Nylon is lightweight and strong, and particularly wear-resistant if you're active in sports. It also is ideal for the flexible, long-lasting wraparound eyeglass frame.
Although it's not super-strong, zyl, short for zylonite, gives you a designer eyeglass frame in whatever color you might want, such as Nine West's NW 11. Want your eyeglasses frame to match Marcia Cross' hair on “Desperate Housewives”? No problem!
The most durable plastic eyeglasses frame we've seen is On-Guard Safety's with attached wire mesh side shields.