This is the small circular needle clip, which was particular to the original Amal RN (Remote Needle) models - it being of a shape to retain the needle in small circular chamber offset from the main throttle slide.
This is unlike other carb needle clips, in that it is small and does not foul the side wall of the RN needle chamber - as can be seen from the accompanyning photograph.
Note: we can also supply the special 'milled' needle holder that was screwed to the slide of original Amal RN type carburettors, as shown in the photo - for these See Item 0962.
Update Dec 2020: We are in the process of manufacturing a new batch of high quality throttle slides to fit original Amal TT carbs. We will also be making a small batch of Amal RN slides (Item 0961), which are of the same type as the TT slide, but with the addition of the milled needle holder. Please email on firstname.lastname@example.org if you wish to reserve one of these slides - as they may not be available for long.