The clamp slides nicely over the seat tube - no play. I emailed the UK source to see if they would sell a bolt, washer, and "barrel nut". I didn't know the proper name, thanks for that.
The seatpost is a good fit into the seat tube as well.
I like the barrel nut design, rather than threading into alloy - it should work better when removed/replaced multiple times when adjusting or replacing saddles.
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Dale, NL4T