Bike Magic has a review published on crankbrothers’ Kronolog adjustable height seatpost. The seatpost features mechanical travel movement giving it 5 inches of infinitely adjustable travel settings. Bike Magic seems to have had good success with their test model, noting its reliability during their muck filled test riding.
“Norglide bushings limit lateral play and it’s a well sealed unit. In the two months I’ve been testing it in the depths of the British winter, it’s proved to be adequately sealed. I’ve had no problems at all, it’s still working as smoothly as the first ride.” – Bike Magic
If you’re interested in purchasing a Kronolog or other adjustable height seatpost online, check out Jenson USA’s wide selection.