Institutional series precision bearing donut monotech wheel total lock caster. Zinc plated finish for corrosion resistance. The Institutional Series is our most expansive medium duty product line. Constructed of high strength steel for added durability, the Institutional Series is bound to meet any of your medium duty mobility needs.. Ideal for hospital equipment, utility carts, store fixtures, institutional equipment, office equipment and food service. /8-inches diameter nut and bolt axle.