I have drilled marbles and granites so far with great ease. Don't hesitate to spend the money. The hole is made so quickly that it really is worth the cost.

Good quality drills. I drilled granite tiles relatively easily. I started with the 4 and as soon as the hole was made, it opened easily with the 6. I had previously used a similar drill of another brand on the same granite and it melted due to the temperature. These drills also heated up, but they didn't suffer any damage. I recommend them.

I would like to add that it is good, while drilling granite, to fill a bottle with water and have someone pour a little water in front as you drill, in order to lower their temperature and make them last longer