Review on Diameter Mandrels for Plywood, Drywall, and Plastic by Fritz Wiest

I bought these at a good bargain price. I needed a 4" hole saw. I found that one hole saw was enough for the whole set. I used a 4" hole saw to make two holes in two 1/4" pieces of clear plastic. I noticed right away that it was wobbles when turning as if it's not perfectly round. They seem to cut well. After I cut all four holes I noticed that that's where the drill bit starts to warp. In the picture with two hole saws you can see the hole after bottom is deformed. I feel that the overall quality of this product was not very good. I was doing my job, I just didn't expect the tool to already try to break. I hope this helps you make a more informed decision hold true. .