●Low profile spacer for bicycle and headset ●Inner diameter: 1.1 inches (29 mm) (1-1/8 inch standard), outer diameter: 1.3 inches (34 mm) ●This is a 6 piece set of 0.01 inch (0.3 mm) thick, 0.04 inch (1 mm) x 1, 0.08 inch (2 mm) x 1, 0 ●6 low profile spacers help fine tune the thickness ●Made of aluminum that is strong and strong against compression