It's not that exciting a mod, I must admit, but it's a pneumatic preload collar.
Essentially, when you use a hydraulic preload collar, it doesn't adjust in a linear fashion. One turn of the adjuster wheel, doesn't equal the same amount of preload, for each turn.
The preload rings are perfectly linear, but a little difficult to adjust. But, very light.
The pneumatic is also 100% linear, very easy to adjust, but (comparatively) heavy.
As the topic was so exciting, I did a YouTube video on it will share.