0.25g HPA High Power Airsoft Bio 4000 BBs - Bottle. Fully biodegradable high-grade airsoft BBs for use in upgraded guns. These have a cult following of users. Great BBs with a proven track record. If you need bio style, consider these. One of the highest quality .25 BBs made in the market. Highly polished for your barrel's pleasure. Comes in a refillable bottle.