Simply tighten the topmost knurled nut to compress the rubber for a snug fit.
The Series #20 features an innovative expanding stem that can easily adapt to the inside diameter of the opening, allowing for a secure fit in round or square tubes.When searching for a reliable and durable solution to your caster needs, look no further than the Service Caster Series 20 expanding stem polyurethane wheel casters. Listing is for a set of four (4) Service Caster Series #20 3/4" expanding stem swivel casters, two (2) with top locking brakes, with 3-1/2" diameter by 1-1/4" wide gray polyurethane wheels capable of supporting a total weight of 1,000 lbs. For added security, further compress the rubber with a wrench via the nut under the swivel raceway.