Rock-N-Roller RCSTR4X2 Ground Glider Caster with Brake (2-Pack) - 4 x 2"The pack of two 4 x 2" Ground Glider Caster with Brake from RocknRoller MultiCart is a replacement caster system with nuts and lock washers for the R2 utility cart. Each caster features low profile, no flat tires around a durable and lightweight hub. When in use, they provide low rolling resistance, pneumatic like cushioning, and wide load dispersion over soft terrain. Compatible Models R2 Specifications Size 4 x 2" 10. 2 x 5. 1 cm Packaging Info