The Auto-X-ZTS RSB has been around since 2004. There are a couple dozen pretty serious autocrosser and track-day racers that use it. It is a 'natural' 24mm (actually 15/16"); it has 3 holes for endlink placement--which are heim-joints. The middle setting is the natural setting and then it can be made one setting stiffer or one setting softer--roughly +/- 1mm...or 23/24/25mm.
There is also a 7/8" version for cars with softer springs...its approximately 3/4mm +/-...or 21.5/22.25/23mm.