It's a pretty good amount of puffing. Enough for powerhobby to warranty the battery via picture. Maybe 3-4mm? That's a guesstimate. But I can squeeze the air out....that's what's messing with me big time lol. I've never been able to squeeze the air out of a lipo. And I can do it every time i run it and it puffs up. It squeezes out to perfectly flat. As far as loosing punch, these packs still flip my xxl2e on it's back at 3/4 throttle and it's a big truck.