—— Diamond Drill Bits are made of carbon steel and coated with nickel to resist corrosion. Diamond hole saw creates a high precision, smooth cut with no broken edges. Reduced drill speeds, low drill pressure and increased use of water lubrication will extend drill bit life considerably ——15 Diamond Hole Saws 6mm/0.24" 8mm/0.31" 10mm/0.39" 12mm/0.47" 14mm/0.55" 16mm/0.63" 18mm/0.71" 20mm/0.79" 22mm/0.87" 25mm/0.98" 26mm/1.02" 28mm/1.1" 30mm/1.18" 40mm/1.57" 50mm/1.97" ——No need to worry about scratching your tile when drilling the hole. Our Adjustable hole saw drilling guide with suction cup and 4 bearings will hole the diamond hole saw still during the process. From 6mm to 50mm all the hole saws can fit in this guide. ——The large clearance holes on drill bit help cooling with water and rinse chips and other particles from the borehole, ensuring smooth cut and speed up drilling. When debris gets stuck in the hole saw,the clearance holes allow you to use the screwdriver to pry it out. ——This diamond hole saw and guide set is a nice set to help you with home modification, wine bottle craft, glass or procelain pot modification. No matter you are a diyer or family handyman, this set is all you need.