Billet alloy fuel cap breather.
Replaces the great lump of rubber pipe.
To get them to sit super flush with the cap as shown in the above picture we cut off the top of the plastic tube on the cap.
Push on fit, but is very tight.
Some caps will more likely need a small v cutting into the plastic or the nipple end trimming off to enable the best fit. (especially if it is a new cap, it they were not super tight then on older caps they would simply fly off!) Mitani breathers are just the same.
 
Discontinued- so what we have left is all there will ever be.