I got an hylix that works like that. Both sides are slightly conical and clamp on the seatpost, as you tighten the crossing bolt everything clamps into place.
Setting the tilt on these is ass, took me a while to stop mine moving, but others may have better experiences.
Thanks. I think the clamps on those look a bit industrial.
Has anyone used something similar to the below? I can’t work out how that clamp works.
Why does Aliexpress always bring up the Spanish site when I try to use it on my phone?
https://m.es.aliexpress.com/item/1005001720228091.html?trace=wwwdetail2mobilesitedetail&spm=a2g0o.productlist.0.0.324c4ca6fCWgE8&algo_pvid=b4416d53-9233-4b9d-ba1b-6e45274caa82&algo_expid=b4416d53-9233-4b9d-ba1b-6e45274caa82-7&btsid=0b86d80216150387210573391eacec&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_