The stem of this caster wheel is 1 3/8″ OD (#6 tube) with a 4″ length. It has a double safety margin built into the load rating. Our wheel is heavy duty, load tested to handle 500 pounds with a 8-to-1 safety margin. The scaffold caster wheel is an 8″ cast-iron wheel with a rubber overlay that is 2 inches wide and over an inch of rubber covering the iron caster wheel. There are ball bearings in the pivot mechanism to handle high loading. Double zirk grease fittings. Double lock to maintain rock solidness. Locks to prevent wheel pivot and locks to prevent the scaffold caster wheel from rolling. Upper steel body is galvanized. Hole location on stem is 2.5 inches from the base.