Although DAMO Dry / Wet Core Bits are designed for use on the job site without using water,wet cutting is recommended whenever possible. They fit on high-speed angle grinders with a 5/8" -11 spindle. Adopting the Vacuum Brazed Tech., they provide the best cutting performance and can drill through the toughest 1-1/4" granite or engineered stone countertop. They can be used to drill the faucet-mounting holes in countertops and vanities. They can also be adapted for use in construction trades wherever holes are needed for water, gas and electrical piping, especially when natural stone, concrete or ceramic tile is already installed. We recommend a template be used when drilling free-hand and a scrap piece of stone be clamped under the stone to prevent excessive chipping on the backside of the stone. Available in 1/4",3/8",1/2",3/4",1", 1-1/4", 1-3/8",1-1/2",1-3/4",2"and 2-1/2" sizes.You may buy seperately our core bits adapter to use with the normal electric hand drills which take 3/8" shank.We DAMO Diamond Tools, LLC holds exclusive distribution to DAMO Trademark products as you can see clearly marked from the picture on the product listing.