It's held on with a 24mm nut.

It's straight off a Mk1 Golf. All Mk1 steering column's incl. cab's should be the same. It was just the indicator & wiper stalk's that changed.

Here's the boss next to a factory MK1 GTI steering wheel.





Next to my race steering wheel with another brand boss kit.

The Momo boss has a depth of 86mm & the race one is 88mm




Hope this help's.