Set 11=20mm, 25mm, 35mm, 50mm, each size 1pc. Multi-purpose drilling for granite & marble, masonry, concrete, tile/ceramic, glass, hard plastic. Special Designed with Hole in both Sides of Drill Bit for fast Removing Stone Chips and Improve drilling efficiency. Dry drilling without water, Use water for longer time. Vacuum Brazed diamond technology provide very high efficiency, cuts faster, durable and sturdy.