Had too look them up too see what they are actually used for lol....
Easton Broadhead Adapter Rings were developed for carbon shafts to provide a larger mounting surface when using broadheads with O-ring and other compression-based blade retention systems. The larger mounting surface allows O-rings to compress rather than roll over the top of small-diameter inserts. In addition, the adapter ring provides a smooth, tapered fit from the broadhead ferrule to the insert. Each Easton shaft has a specific size of a B.A.R that needs to be used with that particular model and spine size. Locate your specific arrow model and spine size to determine the correct B.A.R. for your set up.
DO I HAVE TO USE A B.A.R. WITH MY BROADHEADS?
Easton recommends using the broadhead adapter ring (BAR) if required by the broadhead manufacturer. Broadhead Adapter Rings are required for fixed broadheads that utilize the face of the insert to support or hold the blades in place. Broadhead Adapter Rings are required for mechanical broadheads that use the insert as a stop for the blades after the broadhead has opened.
So I guess if your broad head manufacturer recommends them then you will probably need them... How they affect arrow flight? No idea....
So what's the purpose of my post? I'm bored lol, but I did learn something lol....