Safety razor entitled "Fuck Everything, We're Doing Five Blades" predicted the release of five-blade cartridges, two years before their commercial introduction. South Korean manufacturer Dorco released their own six-blade cartridge in 2012, and later released a seven-blade cartridge. Gillette has also produced powered variants of the Mach3 (M3Power, M3Power Nitro) and Fusion (Fusion Power and Fusion Power Phantom) razors. These razors accept a single AAA battery which is used to produce vibration in the razor; this action was purported to raise hair up and away from the skin prior to being cut. These claims were ruled in an American court as "unsubstantiated
Straight razor called the "belly", and the area between the ridge and the cutting edge which is more hollow i.e. with a smaller radius of curvature. These two beveled areas have different curvatures and in a well-made razor they transition seamlessly in the ridge (belly) and the cutting edge respectively. Sometimes there are three bevels. The ridge stabilizes the blade against torsional flexing in a direction perpendicular to its longitudinal axis by acting as a lengthwise spine for the blade. The distance between the ridge and the back of the blade is inversely proportional to the hollowness of the blade and is