X-lock 4 blade system ensures blade retention on impact. One-piece ferrule for maximum accuracy and consistency in the field. Individually spin-tested for optimal down-range flight performance. Practice blades included. Ultra-sharp replacement blades included.Features:X-lock blade system ensures blade retention on impact;.031 thick ultra-sharp replaceable razor-sharp stainless-steel blades;Individually spin-tested for optimal down-range flight performance;Practice blades included ultra-sharp replacement blades included: one set;1 - 3/16" cutting diameter 100 grains