The major advantage of American component manufacturers White Brothers' air-sprung suspension seat post is that a chamber of compressed nothingness is obviously lighter than elastomer or coil springs.
The air shock also allows infinite adjustment of the spring weight within the parameters of the pressure settings. And adding more or less cush is much quicker when all you have to do is add a few PSI with a standard shock pump, rather than strip, remove and replace elastomers and then rebuild other posts. That said, the air valve is inconveniently placed at the bottom of the post. This means that it's hidden away in the frame, and even though this toy should be a fettler's delight, few are going to bother taking the post out, adding 5 PSI and putting it back in again to see if they can feel the difference.
The clamp falls into the tried-and-tested 'two bolts front and rear' camp, and they're splayed outwards slightly so setup is a doddle for even the fat of thumb. And it looks good too, with distinctive graphics etched onto the black aluminium post and a rubber boot to top things off nicely.
But we were rather disappointed with the post in action. Initial setup was complicated by the fact that the recommended shock pressure for the tester's weight was way too low - we eventually ended up doubling the PSI before the shock would support the (average) rider's weight, taking the post in and out of the frame for each and every alteration.
Though we squashed in many more saddle hours than White Bros recommended for bedding in, the travel remained stiff and notchy throughout. We're not sure whether the three brass bushings simply take an exceptionally long time to bed in, or this is just a 'feature' of the air shock, but it certainly doesn't feel like the luxury option the price tag indicates.