Callaway big bertha os graphite irons big bertha os irons promote more distance in an entirely new way led by extraordinary light and strong exo cage that allows us to strategically position weight to increase forgiveness and helps our industry leading next generation 360 face cup produce even faster ball speeds and more distance more forgiveness and ball speed from new exo cage technology the uniquely light and strong design of the exo cage allows more weight to be positioned in strategic l