I could have found much more expensive bits than these but my project was small and I needed the bits in a hurry. They worked great on very demanding solid wood work, although they didn't last very long and eventually overheated and broke. I expected this and was very thankful I didn't pay much for it as I'm sure the expensive ones will go broke and cost me more for the same job. If you use them on thin or soft material they will work for you. Also, I have 1st Gen Rotozip and they eat bits by default! These parts arrived very quickly and I got my job done on time which is the most important thing for me. If you want perfect beats, go to the Rotozip site and spend $.