Thunderweb drill bits have an internal core which thickens towards the back of the drill bit, which adds strength resulting in less breakages. 135 degree precision point. 19 piece. Contains: 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, 9, 9.5, 10mm. Supplied in a plastic case.