Garage Door Rollers Quantity of 12 . 2" 13 - Ball Nylon Rollers 2" 13 - Ball Nylon Rollers .SEALED BEARING. 12 Rollers Quanity of 12 rollers in the package . 7/16" ( 11.09") SHAFT THICKNESS. 1/2" WHEEL THICKNESS 1-13/16" WHEEL DIA. 4-1/8" SHAFT