These powerful heatwraps truly do what they set out to do-they provide at least eight hours of heat (my husband & I have been afraid of wearing them for more than eight hours since it only says up to eight hours!). My husband wears these on a daily basis at work (he does a lot of heavy lifting) & he said that the only way that you know you are wearing the wraps is from the heat that they emit-he said that the wrap itself is very lightweight & does not provide extra bulk under your pants. Even after wearing the heatwraps, your back & hip area are still hot! What we like about the heatwraps is that you can be mobile when wearing them-you are not constricted to a bed or chair like you are when you use a heating or massage pad. The only negative that we have is that only two wraps come to a box & we wish there were more.