I bought 2 packs of these 25mm diamond coated hole saws for a fraction of the cost of each at the store. I didn't think I would have to spend so much money on something that I would use several times a year. I was very satisfied with the performance of the instrument. I cut a template hole in a piece of plywood using a regular hole saw, gently pressing it against the tile, shaking off the water around the drill bit while I cut the hole. The beat still looks intact. Maybe users who had problems with abrasive material used the tool dry and overheated?