Zipp Headset Spacer Set UD Carbon (4mm x 2 8mm x 1 12mm x1 30mm x 1)Zipp Headset Spacer Set UD Carbon (4mm x 2 8mm x 1 12mm x1 30mm x 1). Imprecise spacers can cause your headset to loosen affecting bike handling and component life. Lightweight and precisely parallel Zipp carbon headset spacers are precision ground to keep your fork secure through every twist turn and bump in the road. 1 1 8" diameter in 4 (x2) 8 12 and 30 mm heights UD carbon fiber finish TECH SPECS Color Carbon Material Carbon Defined Color Black S.