It is smooth. I confess - I don't know too much about headsets, having never bought one. All my building experience has been on Japanese bikes, and they all have (it seems!) interchangeable headsets. I've always gotten by with recycling and re-using from my scrounge pile.

The only thing I failed to consider was stack height - just forgot plain forgot about it. I got lucky with the Levin, although it was about as close a call as it could be. Good thing the lock washer is recessed into the adjustable cup!!

Also - the Columbus fork did not have a groove for the lock washer tab. I had been using a 3 notch lock ring on the other headset, but it was too thick to use with the Levin. So, took my dremel and just knocked down the threads on the back side a little bit and squared up the edges of the new groove so the tabbed lock washer would fit nice and snug.

Worked great, but I wasn't real jazzed about taking a dremel to this fork.....