This is a post with some heritage behind it. USE's SX has been around for years, and the design has changed very little over that time - a case of if it ain't broke, don't fiddle.
The clamp is rock solid, light and elegant, although it did require testers to grow a third hand to aid fitting because the various parts of clamp and cradle all made their escape bids in separate directions. Once setup though, it was completely secure throughout, with no hint of a slip.
The black anodised 7075 aluminium post, with neatly laser-etched logos and markings, hides a combination of elastomer and coil springs, which deals with the suspending. The coil springs are suppler than the elastomers and deal with smaller hits, while the elastomers provide a basic form of compression damping and take care of larger bumps. Four different spring/elastomer weights are available from USE's legendary customer service, as are full service kits to deal with the inevitable bushing slop that will occur over time.
Preload is adjustable via a 6mm hex bolt located at the base of the post. Once this was tweaked, the SX's annoying tendency to bounce us off the top of the saddle disappeared and we were left with a post that did a good job of tidying away roots and bumps without making any fuss about it at all.
Ordinary may be a little boring but in this case it certainly does the job. It's just a shame that the time-honoured clamp design is so tricky to install.