●12 piece set: 2mm x 3pcs, 3mm x 3pcs, 5mm x 3pcs, 10mm x 3pcs ●(28.6 mm), Outer Diameter: 1.3 inches (34.9 mm) ●Material: Carbon head spacer, high hardness and not easy to deform. Lightweight with superior strength, toughness, and corrosion resistance ●High Quality: CNC processing, spacer diameter is precision ground to eliminate imbalance, ensuring stability and accuracy ●Applications: Adjust the head height of low bikes, MTB, cross bikes, mountain bikes, etc