This is a set of (6) diamond coated drill bits. You receive a set of (3) diamond twist bits 1mm,1.5mm & 2mm. also a set of (3) diamond coated solid bits.All are recommended for drilling holes in sea glass,marble,title & granite. These diamond bits are often used by toy model makers as well as jewelry artist. The combination set of (6) bits will give you the opportunity to try each type. You may fine that one works better than the other, depending on the material you are working with. FREE with purchase are some tips & suggestions that I wrote that you may find helpful. " Drilling Holes in Sea Glass & Beach Stones"