The Pro Shot Shotgun Adapter adapts #8/32 (Rifle) thread to accept #5/16-27 threaded shotgun brushes, jags, patch holders.
The #AD2 is meant to make a smooth transition for the 27 & up diameter rods to accept smaller diameter accessories, such as a bore brush or patch holder. This accessory transitions the smaller diameter accessory in conjunction with larger diameter rods, making it a totally smooth fit.
The #17AD adapter converts #5/40 threads to #8/32 threads and is used on .17 cal. rods to clean tight bore .22 caliber Rimfire rifles. The adapter allows you to use the standard #8-32 threaded rifle accessories with the smaller diameter rod. Not for use on cleaning 17 caliber firearms.
Big Book Catalog, Issue:67, Page:323
Big Book Catalog, Issue:67, Page:324