The NAP Thunderhead is America's #1 selling broadhead. High Carbon Steel Trophy Tip is hardened for the most devastating durability available on the market. Stainless Steel Blades have the exclusive Diamized Edge for a visible super-sharpness you can see for yourself. The patented scooped out Slimline ferrule improves flight and penetration. The original lock ring, O-Ring blade retention system has been proven a million times over. NEW ARCHERY PRODUCTS Thunderhead 85 Grain Broadhead.