The Dremel tool company offers a $20 per drill product, which far exceeds what Dremel offers. Hands down is the best product of its kind. I drill corundum if you don't know it's ruby and sapphire and it's a 9 on the hardness scale and diamond is a 10. And this product is the last, last, and last, it is unbelievable. I am writing this review because I wish I had found it sooner and I know reviews can make a difference and this product is amazing. FYI this is a wet drill product, if you try it dry it won't last long. Good luck in your adventures.