8mm Bore 8mm 30mm 25.7mm 15.6mm 8.5mm 2.2mm. M8 28mm screws are suitable for U-grooved 8mm bore bearing, need to use M4 hexagon spanner to fasten. M5 18mm screws are suitable for U-grooved 5mm bore bearings, use M2.5 hexagonal spanner to tighten.
eBay