Who engineeers this stuff????

isn't that cap for a dresser with air/hydraulic front forks? I would think White bros should have a solid cap replacement. or maybe custom chrome. either way, there is an alternative sealing ring, it's a steel washer with a rubber or silicone seal ring bonded to the ID . we use them a lot on low pressure fuel systems and some hydraulic applications.

Looked thru the Custom Chrome catalog, no luck. Checked Joker Machine, nada. Can not find a White Bros. site, will look again.

I am not a H-D guy so I don't know what all the letters stand for. Custom Chrome as them listed as Wide Glide fork tube plugs....

Would make sense that they are of a pass thru design for a bike with air forks....but other than that why they are drilled all the way thru is beyond me...