Due to its versatility, the No. 4 Smoothing Plane is the most commonly used bench plane. With a 240mm(9.1/2") long sole, it is the ideal size for general smoothing, finish work, trimming parts and other odd jobs. At 2kg(4lb 6oz.), it has enough mass to cut smoothly but is light enough to use without fatigue. The No. 4 is supplied with a 50mm(2") wide lapped O1 blade. These lapped blades have a flatness tolerance of ±0.005mm or better over the working surface, and with an average roughness surface finish of 0.000127mm(5 micro inches) or better.