I have a set of the 'Evol' model on my KX250A5, the Evol has the dual-stage air chambers and adjustable rebound damping. They were originally designed for the Artic Cat snowmobile, the rebound damping was way too much, I sent them to Shane at Hardiman ATV (the Fox importers) to get the rebound revalved.
The problem I see with them is that motorcycles need much lower air pressure than the snowmobiles that they were designed for, with the lower pressure the top-out spring is too powerful and limits the available travel as the shocks won't extend to the topped-out position.
Plus the shocks do not have a short enough compressed length, further reducing travel ..... with the shocks bottomed-out the wheel was still 4" from the mudguard.
The quality of them appears fantastic but I am selling them as I think they will take too much work to get them working. They cost me $1100 but I'm selling them for $600, they've never been used.
