The 150 Grit BW7 (photo shown is 150 Grit) is a wheel shaped diamond bur. The approximate head length is 3mm, and the approximate head diameter is 13mm. This bur is great for grinding or carving all types of stone, glass, tile, metal, wood and more... The 150 Grit is intended to be used for cutting or grinding, and works best for roughing out your basic shape and doing your design work. The 150 Grit cuts most types of materials while reducing chipping and pitting of the material being cut. As with all Lasco Diamond Burs, the 150 Grit BW7 is a high quality, durable, 100% Natural Diamond bur, and is made in the USA. The BW7 is also available in 40 Grit, 80 Grit, 150 Grit, 200 Grit, 400 Grit, and 600 Grit.