I’ve got the Forca one (30.0 seat tube, so only option is to shim a 27.2)
It is very basic, and quite cheap too. It’s cable operated, with a couple of springs, no damping, just two little pegs to limit top and bottom. No way to adjust how far up/down it can go.
When I got it I wasn’t impressed, depsite it being cheap it looked flakey even for the price, primitive and just felt clunky.
However, after 11hrs of the Transvesubienne, some of the most brutal riding I have ever done in some horrendous weather, it was still going when all the fancy ones had long since packed up. And it was a doddle to service afterwards.
If I had to make an analogy it would be like an old Series 11 Landy. Very primitive, nothing fancy, doesn’t look like it should work. But keeps going and nice and simple for home mechanic.