XHD stands for Extra Heavy Duty and we mean it. Thicker alloy barrel, 5/16" spring steel shaft, trigger mechanisms are carbide tipped and all models are equipped with 5/8" Hi-Mod bands that feature stainless wire wishbones. The XHD is the gun of choice for commercial and hard-core shooters; to these guys it's a tool...not a toy. Three bands and a heavy shaft will punch through just about and fish, which is why the Shark Research Institute depends on the XHD for tough jobs like radio tagging 40 ft whale sharks. Go big, go XHD.