I use the Flexi Shaft to drill holes in my stones & with the silversmiths kit. The diamonds bits have lasted many drillings, It depends on how hard the stone is and if you push to hard, that can be the reason the diamond would wear out faster. It runs smooth in your hand with virtually no vibration, which is great for long time use. You can use it with all size bits as the hole size of the flexi shaft can transition from .5mm to 1/8 inch sizes. It transforms your Jooltool into another tool & I love it!