Rare item for older style BB’s, designed to fit inside BB shell between cups to prevent water and debris getting to the bearings.
With older steel frames, there is a greater chance of debris from inside of tubing falling into BB shell damaging it.
Top left Shimano Black color: $ 15
Top right Shimano Dura Ace: $ 20
Bottom left Campagnolo: $ 20
Bottom right Hatta: $ 20
All are the same size and will fit English or Italian thread BB’s.