Description: Please note， this is 5mm bore pulley. These pulleys can be used in Ultimaker， Ditto or other 3D Pinter designs with similar kinematics. For 3D Printing applications， GT2 2mm belt system works better than T5， T2.5， it gives better smoothness and accuracy of positioning， resulting in better printing quality. Specification of timing pulleys: Tooth number: 20Tooth pitch: 2mmBore diameter: 5mmFlange: doubleTooth width: 7mm ( Very Suitable and good for 6mm synchronous belt ) Specification of timing belt: Color:blackPitch: 2mmWidth: 6mmMaterial: fiber reinforced rubberLength: 2m Package included: 2 x 20 Teeth GT2 Aluminum Pulleys 5mm Bore1 x 2m GT2 Timing Belt1 x Allen Key