I found this on ToolMonger:
Hold-downs can be very helpful in the shop, but did you ever stop to think what would happen if your router bit or table saw blade — or any other cutting tool designed for soft materials like wood — came into contact with a metal hold-down? At best you’d have a damaged hold-down, at the worst flying shrapnel.
If the last paragraph got your imagination working, these composite hold-downs from DE-STA-CO are starting to look pretty good. The lightweight glass-reinforced nylon can produce a holding force of 200lbs, but it won’t damage your tool. The arm opens 100° to make placing and removing parts easy, and you can adjust the nylon spindle about 1/8″ vertically and 1-1/2″ along the lever arm. The hold-down comes with a slip-on neoprene cap.
You’ll pay about $10 for one of these composite hold-downs, which is in the ballpark of a similar metal version.
Composite Hold-Down [DE-STA-CO]
Composite Hold-Down [McFeely's]