Attributes . Ice Hardened Cryogenically Treated For Up To 50 PCT Longer Life; Optimized Tooth Form For Up To 2X Faster Cutting; Wide, Angled & Offset Slots For Easy Plug Access; Bi-Metal Construction With 8 PCT Cobalt For Increased Wear Resistance; Works With The Following Arbors: 49-56-7240, 49-56-7250, 49-56-9100, 49-56-7055, 49-56-7040, 49-56-7140 & 49-56-7150; Rpm Mild Steel: 80 RPM; Rpm Stainless Steel: 40 RPM; Rpm Cast Iron: 55 RPM; Rpm Aluminum: 120 RPM . Names