5/16" inch (7.94mm) Ball Bearing with 3/16" inch (4.76mm) diameter integrated 1/2" inch (12.7mm) Long Axle, Pin Diameter is 3/16" inch, Bearing Outer diameter is 5/16" Inch (7.94mm), and Width of the assembly is 1/2" Inch (12.7mm Long), Bearing is made of Chrome Steel.