TUNGSTEN CARBIDE burs can be used on most hard materials: including steel, aluminium, cast iron, stone, ceramic, bone, hard wood, acrylics & fibreglass. Also ideal when used on soft metals such as gold, platinum & silver as 3 times harder than steel & won't blunt as easily. INVERTED CONES can engrave angular lines, help texturise as well as are used in various setting applications.