Steel recessed weld bung for -10 port plug. Commonly used for a drain plug on a custom fabricated rear end axle housing. The -10 port is more low-profile and doesn’t weep like typical pipe thread fittings.
This bung recesses the -10 port plug so it can also function as a jack stub on the rear end housing and not damage the plug.
Can be used for various other applications requiring a -10 port plug or fitting.