Waldhausen's new rubber bits are made of high quality polyurethane. Please make sure only to use a rubber bit on horses producing ample saliva. Rubber is a soft material and is subject to natural wear and tear in the horse"s mouth. Wear can be increased if the bit is fastened too high up in the horse"s mouth and horses can chew the bit with their back teeth. This is why you should make sure the bit is fitted correctly.