These cups work great but don't last long. After reading other reviews I decided to order them anyway, not knowing what to expect in either a worst or best case scenario; I chanced the outcome.They are small indeed but that was okay with me since I was working with limited space. However, buyer beware of their small size.I only used the diamond cup one to grind appropriately 3 sq. ft of 20 year old mortar before re-tiling (on a concrete surface), and when finished, the diamond cup was worn almost completely. There is probably about 3 mm left in the cup, but I got the job done. Now I have a little "meat" left on the cup and whole new disk to work on something else eventually.If you're planning on working on a larger area, these will not last you more than 4... maybe 5 sq. ft. (on a concrete surface) on the cup alone.They grind excellent and that's why I rated them a four. I'm not rating the wear and durability since I knew beforehand that I only needed them for a small project and other reviews warned me not to expect a long life with these . If I were to rate the wear and durability, it would probably be a 2 at most, but that wouldn't be fair since I knew beforehand that it was only purchasing them for a small re-tiling job. If you need a diamond cup that will take on an entire floor and last a long time, buy yourself DeWalt.