0.12g Biodegradable airsoft BBs (a.k.a "bios") are usually made from a plastic called polylactic acid or polylactide (PLA). PLA plastic is constructed from natural resources and renewable materials including corn products and certain starches with a molecular formula of (C3H4O2)n.0.12g PLA airsoft BBs cost more than ABS BBs but are environmentally friendly, are more water soluble than ABS BBs, and break down into water and carbon dioxide in about 47 to 90 days in industrial recycling facilities or a bit longer under the right environmental conditions outdoors. Most outdoor airsoft fields require players to use these types of 0.12g biodegradable airsoft BBs.