Abstract: According to the preferred form of the invention, a pair of thin wheels is rotatably mounted in the bottom of the body of a caster or other load supporting wheeled device in a bilaterally symmetrical array. Each of the wheels has a downwardly facing outer terrain-engaging surface in the general form of a frustocone, and an upwardly facing inner annular bearing surface which is opposed by a complementary annular bearing surface on the bottom of the body. Preferably one or more antifriction washers are interposed between the wheel and body bearing surfaces. This arrangement provides large bearing surface areas which are located directly above the lowermost apex of the frustoconical terrain-engaging surface so that direct vertical loading is applied through the bearing surfaces to the terrain-engaging footprint of each wheel, thereby avoiding cantilever action, avoiding any need for rollable bearings, and permitting the wheels to be very thin and of extremely low profile.