The Mayfly is a cheap Chinese knockoff of the Renzetti. I had the first version with two screws for jaw adjustment, but never had the lever action vise. The vise is adequate, but rough, needing some polishing and refining, but is entirely adequate for tying and the price is right. For not much more, you can get a true rotary Danvise for a good price at H&H, they also cary the EZ vice which is very similar to the Mayfly and they are a sponsor here. Just sayin. PADDY