Colson 4 series swivel plate caster 4.06109.539 brk4 – nylon total lock brake 6″ dia. 1200 lb. Cap. zinc plated glass filled nylon wheel for easy mobility without damaging concrete floors will not absorb water like phenolic wheels will straight roller bearing in wheel zerked raceway & axle for easy maintenance total lock brake locks the swivel raceway and wheel simultaneously standard top plate