Suitable for scraping wood, metal and concrete. Tungsten carbide blades remain sharp for much longer and last 50 x longer compared to conventional steel scrapers. The blades are precision ground and slightly convex, preventing scratches on the work-piece. 50 mm and 65 mm blades can be used on both sides, the triangular knife can be used on 3 sides. 442: Spare blade 50 mm for the scrapers 650 and 440. 451: Spare blades 65 mm for the scrapers 650, 665 and 450. 449: Spare blades triangular 25 mm for the scrapers 625 and 448.