Does anyone know for certain which Abus Nutfix seatpost clamp will fit a CCS?

Or even how the Abus Nutfix clamps are measured, inside or outside diameter?
My CCS has a seatpost diameter of 27.2. After much searching, somewhere online I saw a recommendation for a 28.6 clamp, so that is what I ordered. I could see that it was too small without removing it from the package, so it is going back. I called Abus for their recommendation, and they said that the 28.6 is for steel frames, that a 30 should work for my aluminum CCS, so that is what I am ordering now, but I have a feeling it will be too small, too. Every time I get it wrong it costs me almost $10 for shipping.
I measured the 28.6 Nutfix clamp in the package, and it really looks like it is 27.5-28 outside diameter. I can't tell if the clamp is opened or closed without opening the package.
I measured the CCS' stock seatpost clamp (while closed), and the inside diameter is 30. The outside diameter appears to be 35.
Amazon offers the clamp in 28.6, 30, 31.8. and 34.9. It looks like there is also a 34.98 available from another seller.
If the Nutfix measurement is actually the outside diameter of their clamp, I could potentially spend $35-50 or more just in shipping, and still not have a locking clamp that fits?!
If anyone knows which Nutfix skewer to replace the front quick release, that info would be helpful too. I know someone else has asked before, and got no answer.
Thanks, everyone!


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31.8. When i got the ebike , the guys from the shop did it otherwise i would have been doing pretty much as you did...


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I use ABUS locks (Bordo 6500 AND 37RK/55 paired with Laclede 3/8" Square "Lockdown" Security Chain) for my locks, but for seat/stem/nut security I have been using

Sizing is as simple as reading the number of the hex wrench that you use :)

I had to change the seatpost clamp and front axel to be non-aluminum sockets (not magnetic on the original RCS)

It was too late to change my order, so I ordered the 31.8. When it arrived, at first glance it was a hair small, but we got it on there. It was (literally) a bit of a stretch. My husband used to work at our lbs when he was young, so he knew how to get it on there without hurting it, or the frame. Otherwise, I would have had to have it installed at the shop. It works great.
Thanks, Neil!
I have 2 Abus locks, one is the long U-lock and the other is the extra-long folding lock, plus the nutfix seatclamp. I would like to add a lock to the front wheel, and maybe the rear, eventually.
I just realized, reading my initial post, that I failed to mention that I contacted Abus USA by phone to begin with, but that they could not answer my question. The person that I spoke to said that he had made the same mistake himself when he bought a clamp for his bike. He did say that the first wrong one that I purchased was for steel-frame road bikes, I think.