1-1/2 Inch Cutting Depthelectron Beam Welded M-2 High Speed Steelspring Steel Back, Positive Rake Toothcutting Edge Rc 63-65, Vari-Tooth Designsuggested Rpm:80 For Mild Steel, 40 For Tool And Stainless, 55 For Cast Iron, 110 For Brass And 120 For Aluminum.