I don't know but when 6 feet in front of a cement wall they explode apart and leave a white mark on the wall these are nice because they biodegrade really fast but they are a hair smaller so they don't shoot as hard but for how fast they degrade i don't mind ........... BUT these biodegradable bb's are the best on the market for power and acuracy these take like a year to degrade though but they are 100% biodegradable and where tested in lab test as all those KSC and excells and muriu's and a few others where not they contained plastics in them so they where not biodegradable even though they said they where... for long range combat with accuracy pluse inviromently freindly these are the best yet available .

They are called BioTech Biodegradable BB's .20

http://www.garliccityairsoft.com/pro...products_id/56