Arca adapter that attaches to the right side objective. Arca plate is centered to keep your binoculars centered with the pivot point of the tripod. The centered plate has also a lowered profile to help getting your binoculars in and out of your chest pouch.
To select the required diameter, please measure OUTSIDE DIAMETER of the objective at the location where you want the ring to be attached and select size that is the closest in the menu, for example a 56mm mount will fit from 55.5mm to 56.5mm