Rounded nylon bristles (soft) for superior cleaning. Ergonomic handle made from 100% corn starch (non GMO!). Disposal instructions: 1. Break off toothbrush head. 2. Discard thoughtfully. Check with local recycling programs if suitable (nylon is recyclable). 3. Place the rest of the toothbrush into your compost. Please note: the Jack N' Jill bio brush cannot be sterilised in boiling water or microwave.