These virtually unbreakable graver handles have cores of Thermo-Loc® fixturing compound which holds gravers securely without the need for drilling. Simply warm the handle in hot water or heat the tang of your graver or other steel tool and insert it into the handle. Once cooled to room temperature, the Thermo-Loc® hardens around the tool, keeping it securely in place. To switch tools, simple warm the Thermo-Loc® core to 160°-180°F. The set includes 4 different color handles.