Skull is made of steel and comes with 1/2 split ring and 5/16" black button head bolt and nylock nut 
Skull Measures 2 1/8" from the center of the 5/16" mount hole to the center of the ring hole - 2-1/5" H x 2-9/16" W total 
This skull is the absolute best and coolest way to mount your Bell to your motorcycle 
Bell not included