Vented Barrel Bushings

Vented Barrel Bushings I purchased a new Condor from a great guy on yellow clasifieds he had bought a couple vented barrel bushings, with a caliper they measure 1.003 on the O.D and one is .627 for 5/8s od maybe and the other is .477 now keep in mind this is with a caliper not a mic anyway I know this has been talked about I did a search but nothing really came up. I remember seeing something on these being made my quesion is which one gets changed one or both and what do they really do thanks I am new to this Condor I haven’t had a chance to get it ready to shoot but will be working on it hopefully this weekend thanks Eddie Also the one with the bigger ID is polished aluminum the other with the smaller ID seems to be coated or sprayed kind of a sparkly finish.