Diamond drill sizes: diamond drill set includes 5 diameter of 3/4", 1", 1-3/16", 1-3/8", 1-5/8", good quality diamond drilling tool set Steel and nickel coated material: these drill coated hole saws are made from steel and nickel coated material, the drill head is covered by diamond particles, sturdy Clean and accurate hole: can drill a complete clean and accurate hole from hard surface, no broken edges and no tremor phenomenon, long service life, durable Multiple uses: hole saw set can be applied on porcelain, glass, tile, ceramics, stone, granite and other hard surfaces, for most common standard electric drillers Warm notice: please add lubricants or water frequently to avoid sparks while using these coated grit hole saw set, can also enhance the working life by doing this This set is specially made for drilling holes in thicker materials such as granite counter-tops. You can drill 1 1/4″ to 1/38″ in depth with ease. Shank is 3/8″ – common electric or rechargeable drillers can be used. Electroplated diamond coating will wear off if the tool gets too hot. Never let your drill bit run dry. Here is how you could use water to keep the tool cool: a- You can build a mini water dam around the hole with plumbers putty. b- You can choose to spray water on the drill bit. c- Or you can use running water to cool the drill bit. EASY TO USE High Density Poly Insert Included – You can use it as a guide to keep the hole saw in position. We recommend using Oudtinx Diamond Hole Saw Drill Guide. Center pilot drill bits are for wood, metal, etc.; Here is how you can keep the drill bit on target: a- You can make your own guide out of plywood – plastic or even a card board. All you need is to keep the drill bit in place until it makes the initial marks. You can also use the insert as a guide. b- You can start drilling at an angle, with the edge of the drill bit making a C slot and then getting the drill bit up to vertical. c- You can manually guide the drill bit with wet sponge. Please use protective gear.