I echo Kaitlin. the small battlestar seems more effective and useful than the big one. i have both and tried both and find myself using the little bstar a lot more. the big one seems only useful for me in areas which are VERY tight and sensitive to the small bstar (or any hard, thinner device, like lacrosse ball versus supernova).  i can thus use the big bstar to roll my serratus (sensitive due to bone proximity to surface) and also my lateralis which is very tight. everything else is good to go with the little bstar, and the big bstar’s diameter just doesn’t put enough focused force on the muscle.