95 suburban idler pulley

anybody know if there is any kind of spacer or something to do with the idler pulley the ones i see at the parts stores are leaving about an eighth of an inch off the front of the pulley everything else lines up perfect it ran fine but slips off sometimes under the pulley and squeals sometimes. now the part that hangs off split from the rest of the belt and it slips off constantly thanks.

Put A washer behind it the same size as the bearing or slightly smaller it was probably stuck to the old pulley when it was changed and went un noticed

thanks ill try that