The German Style Airbrush Terror Spike Novelty Helmet Gives You that Great Look. The Terror Spike Helmet Contains the Following: (A)Metal Quick Release Buckle. (B)"Y" Strap Retention System for a Secure Fit.(C)4 Ply Fiberglass Shell with Hand Lamination.(D)Fully Lined Liner. (E) Steel Rivets.(F)Your Choice of Either a 4 Inch or 3 Inch Steel Spike.(G) This is NOT A D.O.T Certified Helmet. Airbrush Helmets take around Two Weeks for Delivery. Terror Spike Helmet: Notes: Helmet Sizes:...Helmet Sizes: (Estimates).... Adult:.. Small Sizes are approximately 6-7/8-7.. Medium Sizes are approximately 7-1/8-7-1/4.. Large Helmet Sizes are approximately: 7-3/8-7-3/4.. Extra Large Sizes are 7-3/4 to 7-7/8..