BEMONOC HTD 3M Timing Pulley 60 Teeth 20 Teeth Belt Width 15mm Timing Pulley Belt Set Kit Reduction Ratio 3:1 Aluminum Big Pulley: 60 Teeth bore 8mm; Aluminum Small Pulley: 20 Teeth bore 6.35mm; Belt Model: 3M-285-15; Two shaft center distance: 80mm; Reducer Ratio 3:1; Pitch: 3mm; If you need other bore, pls contact us, there are many other bore of this pulley in store. This one shipped from USA, other bore shipped from China.