First, think about the fact that there are tips on the web about how to "fix" this attachment. That should be your first clue.Faults:1. It's plastic, and not a rigid plastic either. You need rigidity to cut decent circles.2. It slips. The plastic is very smooth allowing the guide to change diameters no matter how much you tighten the knob. Most "fixes" deal with this issue.3. Poorly designed "peg". Rotozip videos tell you to Make a hole for the pivot peg. What the don't tell you is the size of the pivot peg is bigger than any of their standard bits! So you either have to try and round out the hole with the RZ to get the peg to fit (good luck), or you need to use a drill to make the hole the correct diameter.Pro's:None I can think of.Basically, this attachment is a piece of junk.