This was from the Model B16 but may have been used on later models, in principle on some of the machines there was a steel pin on which was a bottom metal bush that locked onto the pin, then two bearings was slotted through the pin and finally on top there was a cap .
A shim was seen on the E16 between the bearings
All these parts are rare now as get broken or lost on machines.
Complete arm sets are cheaper and listed elsewhere.
pack of two