Ultra-Life 2" Nylon Garage Roller with Reinforced 6200Z Bearing and 4" Stem (10 Pack) LIFETIME GUARANTEE: these rollers are specified at 100,000 garage door open and close cycle and we promise to replace any malfunctioning roller for the lifetime of the roller ZERO MAINTENANCE: our sealed, 6200Z bearing keeps out dirt and grime while protecting the lubrication grease for a grand total of zero maintenance required EXTRA QUIET ROLLERS: ball bearing, nylon garage roller wheels are ~75 percent quieter than standard, non-bearing garage rollers EXTRA LUBRICATION: groove on roller to disperse grease over an extended period of time (lifetime guarantee) STANDARD WHEEL and SHAFT SIZE: 1-13/16" diameter, 1/2" shoulder, and 1/2" thick wheel. 4-5/8" long x 7/16" thick steel shaft