Wheel Set Description: One 5.1" diameter Drive Wheel: The drive wheel is CNC machined with 5/8" bore (H7 tolerance). Bore is equipped with a 3/16" keyway and a set screw. The wheel is (2.2") wide. Bore is (1.5") long. The surface of a wheel is truly crowned to insure belt won't jump off a wheel. Please refer to the wheel's sketch for the exact wheel dimensions Two (2") diameter Idler Wheels: Each wheel is CNC machined and fitted with three 1/2" bearings. (Heavy duty 6201-1/2 RS bearings) Bearings are rubber sealed to protect from dust. Bearings are placed back to back (best combination). A 3/8" wide standoff (sleeve) will raise the wheel of the mounting plate. This bearing combination is the best-tested solution against bearing failure as it allows for tightening the mounting bolts without causing any axial force on the bearings (ball bearings should not bear lateral load) One (4") diameter Track Wheel: Each wheel is CNC machined and fitted with three 1/2" bearings. (Heavy duty 6201-1/2 RS bearings) Bearings are rubber sealed to protect from dust. Bearings are placed back to back (best combination). A 3/8" wide standoff (sleeve) will raise the wheel of the mounting plate. This bearing combination is the best-tested solution against bearing failure as it allows for tightening the mounting bolts without causing any axial force on the bearings (ball bearings should not bear lateral load)