Bought these for use on my Foredom rotary tool. They fit perfectly, were easy to install and un-install the rolls. I saw a few people complain that they were loose I'm wondering if those individuals used the bottom nut to tighten the rolls on. The rubber on these unitswill get"fatter" as you tighten the bottom bolt, keeping the sand paper from sliding around. I tightened this prettu tight and never has one burst through the seams I used these on white oak making duck decoy, and they were great. My only negative comment was that while they lasted a long time, they seemed to wear out a little faster than my smaller dremmel sanding drums. This could be because the Foredom is much faster RPM than the drill (which is what they are advertised for). Overall this is pretty close to 5-stars when using with a foredom. If you have a really durable wood, you might want to pick up an extra set of rolls.