The two sample caster numbers below illustrate Hamilton’s significant, easy-to understand numbering system. The numbering system for wheels alone, ordered separately, is even simpler.
For example, a W-620-DB-1/2 defines a wheel only, size 6" diameter x 2" face, Duralast® type, with a 1/2" Precision Ball Bearing. Similarly, if you see W-1235-R-11/4-BS, you will soon know from sight that it specifies a wheel only, size 12" x 3-1/2" moldon rubber type, with a 1-1/4" roller bearing and bearing seals.
Most Hamilton Wheels are made available with a choice of bearing sizes or types to provide broad interchangeability and to meet the wide variety of needs in the marketplace. Hence it is usually necessary when ordering wheels separately from casters to suffix the desired bearing size. But you will rarely need to measure the bearing size of a wheel used in a Hamilton caster, because the complete replacement wheel number is given to you in most of the caster charts in this catalog.