Shaving Sword introduced the 'bonded blade' razor, which consisted of a single blade housed in a plastic cartridge. Gillette followed in 1971 with its Trac II cartridge razor that utilised two blades. Gillette built on this twin blade design for a time, introducing new razors with added features such as a pivoting head, lubricating strip, and spring-mounted blades until their 1998 launch of the triple-bladed Mach3 razor. Schick launched a four-blade Quattro razor later the same year, and in 2006 Gillette launched the five-blade Fusion. Since then, razors with six and seven blades have been introduced. Wholly disposable razors gained popularity
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