My local area games have bio-bb compulsory so I have a lot of experience on G&G bio-bb's and I tell ya, they wipe out every "regular" bb I've tried. .20 .25 .28 are the ones at least they sell here and I'm using the .25. Rather expensive I guess with value running around 25-30 euros a 1kg (3500 bb approx.) bag of bb's. But they truly get the job done! =)