0.20 gram BBs are the most popular weight of BBs offered and are generally recommended for airsoft guns between the 200-300 FPS range. In keeping with the requirements of an airsoft gun, they will all be 6mm round plastic BB pellets. As one of the most balanced weight of BB's they are produced with an optimal density that makes their size to weight ratio to be the most capable BB's allowing them to work for a variety of scenarios and guns. Where lighter BB's would shatter upon contact when asserted by a force over 200 FPS, 0.20g BB's will maintain its structure and flight pattern for guns over 300 FPS. In FPS ranges beyond 300FPS, 0.20g BB's will continue to maintain its structure however its flight pattern (your accuracy) will be more erratic due to increased air resistance.