Specifications: 16 Gear without teeth (Bore 3mm)Dimension: 9mm (height) x 13mm (outside diameter)Bore size: ø 3mmFor Belt: 6mm  Package included: 1 x GT2 Pulley Bore 3MM 16 Without Teeth Idle Pulley Timing Gear For GT2 Belt Width 6MM For 3D Printer,,,,