after buy this product for my roommate , I be able to share it as well . my take be that the shake weight be not really mean to bulk up you arm or really tone you out . this be just a good purchase in the sense of its quality because it be not make cheaply . in term of effectiveness , it be more to tone up you arm before you go out at night on that date or to the club . it do work out you arm but do not expect this to replace gym weight but more so supplement it .