The Porter-Cable 43534PC is a 17/64 inch Bull Nose. The Porter-Cable Professional Edge router bit is constructed of 4140 Alloy Steel, a harder grade of steel than standard cast steel bit bodies. Each bit is annealed and heat treated to Rockwell hardness of 40-45 harder than is possible with cast steel bodies. The bit is precisely ground using computer controlled machining for precision tolerances and perfectly concentric shafts. The carbide tip is made from specially blended micro grain carbide for superior results and long lasting sharpness. The carbide-tipped bit is used to form a full-round bull nose on the edge of wood, plastics and solid surface materials. The cutting profile has additional surfaces for cutting top and bottom fillets.