Just replaced the cables/casings on my Campag Record bike and there is included in the kit (Campag) the metal casing end caps for the brakes/derailleurs. One of the end caps is referred to as a step down rear derailleur cap and has a smaller outside diameter at the none casing end. Could someone please explain since I found the regular casing end cap to fit the rear derailleur and this special end cap was not on my bike when I took off the old cables.