Double ball bearings help the caster rolls very smoothly. Overall quality is much better than those cheap China casters. PU wheel can withstand oil, grease. The PU wheel is cushion so will make less noise on operation.
Bracket K Series is made of steel up to 5.5 mm thickness, very strong and galvanized (Zinc) to increase rust resistance for the bracket. PP-reinforced TPU tires, so moving will not make as much noise as hard PA and PP wheels.