The German Style Mood Spike Novelty Helmet Gives You that Great Look. The Mood Spike Novelty 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 a NON D.O.T Certified 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..