This 3-1/2" x 1-1/4" flat tread thermoplastic rubber premium standard duty institional swivel plate caster with total lock brake is quiet and smooth rolling. Thermoplastic rubber wheels are floor protective and easy to start. The flat tread increases capacity.The 34 Series premium plate casters feature high quality, durable and quiet wheels and optional brakes. Total lock brakes provide positive braking of both the wheel and the swivel section.