Tapered square spikes protrude into a target for the ultimate strike. The size of this knuckle is just right at 3.1 inches and made of aluminum. The finger hole size is complimented by the snug fit in the hand. Overall Length: 3.1 Inches. Ring Size: 16 Max. Construction: High-craft Aluminum, Two Hole. Finish: Electroplated, Black. Includes: Key Chain.