0.25g Mad Bull BIO 4000 BBs.
These are Mad Bull BBs manufactured in Taiwan. Designed to compete against the Japanese airsoft market, they are comparable to the KSC brand BBs. The high quality polish applied to every BB, makes these perfect for use in tightbore or other high tolerance barrels. The heavier weight of these BBs makes them more accurate at distances when compared to 0.20g BBs. Players recommend these BBs for any upgraded AEG, high end gas, or upgraded spring sniper rifle.