Steelex 6in Polyurethane Cast Iron Hub Fixed Caster Plate Mount with Lock. They are excellent for institutional applications because they are extremely quiet will not mar floors and provide excellent control and safety with an easy ON/OFF braking system (stops both roll and swivel). They are also low maintenance and have a tread design which offers good traction on wet floors. These 2" swivel casters have a 2" x 2" plate and 110 lbs. capacity. Package Contents: Steelex Polyurethane Cast Iron Hub Fixed Caser Plate mount Steelex D2559 6in Polyurethane Cast Iron Hub Fixed Caster Plate Mount with Lock