All of the internal rings have been heat treaded and fine machined. If the shaft cannolt be heat treated, it is better to use the internal ring as a sleeve. If the needle bearing and internal ring is used at the same time, the play is a common one and they are interchangeable. Our company also produces the inernal ring with accurate play and produces various internal rings with metric and British systems. IR SERIES SIZE: IR5*8*12~IR130*150*50LR SERIES SIZE: LR7*10*10.5~LR45*50*25.5