Hamilton Standard custom engineered an all-stainless inline caster for a major aerospace supplier. The aerospace company ordered two of these special casters designed for a clean-room environment, each with a carrying capacity of 15,500 lb. The caster stands 10-1/8-in tall and 21-in long, and is equipped with two 8-in-diameter by 2.2-in-wide double flanged track wheels. Four 40-mm double sealed precision stainless steel ball bearings were press fit into each wheel with 1-1/4-in axles.
More detail at http://articles.sae.org/12838 .