from the NAP website:

• High Carbon Steel Trophy Tip ® is HARDENED for the most devastating durability available on the market
• Stainless Steel Blades have the exclusive Diamize® Edge for a visible super-sharpness you can see
• The patented scooped out Slimline® ferrule improves flight and penetration
• The original lock ring, o-ring blade retention system we invented - proven a million times over!
• All Thunderheads come packaged with 6 Ubars for use with your favorite carbon arrows.