I have be use this product for about a week now and it do exactly what it say it do , you feel the burn on you arm and shoulder after each 6 minute workout . I have belong to gym in the past and they claim that what it take 42 minute in the gym you get in 6 minute with the Shake Weight be very accurate ! I see a lot of people panning this product on vary site , but for the price I figure I would give it a shot and it work like a charm ! all I can say be that people who say this do not work never actually try this ! definately recommend this as a good way to get definition in you arm !