The Grabber Heat Treat foot warmers are a non-toxic, environmentally friendly, odorless heat source using all natural ingredients that are non-combustible. Foot warmers provide over five hours of relief for those cold and aching feet. Simply place insoles in any pair of close-toe shoes or boots. The Grabber Heat Treat foot warmers are designed for use inside a shoe or boot where oxygen is restricted. No trimming or peeling is necessary. Grabber Heat Treat foot warmers help fight odor and wetness. Foot warmers are available in two sizes small/medium and medium/large and come in package of two.