Solution to minimize overall height and maximize load capacity. Dual wheel casters also improve stability and swivel more easily than wider-face single wheels. However, this 40mm diameter caster is the most "ugly" one of the Series.
Very thick, that is true for both steel bracket and PA wheel. The caster itself is heavy and have strength to support up to few tons per caster. The Swivel head is combined of Flat and Cone Bearing so you will have no trouble operating.