BSA R-10 fill valve ball retainer 16-7402
This is a brass fill valve ball retainer for your BSA R-10, part number 16-7402. It is designed to hold the ball, spring and guide that form the R-10 fill valve. It comes with an O ring on the body but it does not come with the ball, spring or brass spring guide, you will need to transfer these over from your original fill valve.
These fit all models of the R-10, Mark 1, Mark 2, SE, Limited Edition etc.
Make sure you loosen/remove the screw from the side of the regulator block before fitting/removing the retainer, if you don't you will damage the retainer.
This video shows how to service the fill valve >>here<<