Includes:
Headset bearings (pair)

40.25mm (1 9/16") OD

33.33mm (1 5/16") center hole to receive a fork steering tube

Applications:
Use with headset cup Type B

These are the same bearings in a threadles headset 503100
Bearing center hole will accept a fork with a 28.6mm (1 1/8") steering tube
Works with most cruiser or chopper frames that accept a 1 1/8" headset