I have only used a ยผ inch bit so far and I don't think I used this bit for a total of 15 minutes before the bottom bearing simply broke during use. I've only used this bit for trimming plastic laminate and making a few small ยผ inch MDF cuts before the bearing fails. The lowest durability rating I could give this bit was a one, but if I could give half a star I'd put it in. I'll swap out the bearing and keep using this attachment, but it broke pretty quickly.. I have Wasn't expecting anything better given the cheap price but I didn't expect it would break so easily which makes it value for money Pretty bad. I'm curious if all 4 bearings will be of such poor quality or 5 of his one bearing just aren't what they should have been. Luckily I have loose bearings due to worn out bits so I'll get my money back for its double bearing bits but if you're a person who will only have a few bits I'm not sure about this set as a starting point want.