Replacement part Female 1/4-20 to 3/8 Adapter used on Ball Swivels and L Mounts.
Spotting scopes are like giant levers and a lot of force can be put on the small 1/4×20 threads.
These adapters work like a mechanical fuse in order to prevent damage to smaller/weaker 1/4-20 threads.
In the old days the ¼-20 would just get stripped and it wasn’t really replaceable as it was built into the scope body and was hard to replace.
These new adapters do break as they are weaker (works like a fuse) but the advantage is that it can be replaced unlike if the ¼-20 was stripped out which would happen with a bit more torque.
To prevent breaking this part it’s good to always loosen the locking screw before you make any adjustments and also doesn’t hurt to leave it unlocked during transport too in case it gets a sudden jolt during transport.