If you have any RockShox Lyrik, Yari, Pike or 35mm Revelation that isn’t the top-tier Ultimate series, then you’re totally able to upgrade your fork’s air spring to the newest Debonair air spring and Charger 2.1 damper which comes in the Ultimate series forks.
Then you will virtually upgrade your mid-grade fork up to that top-tier Ultimate Series since you will have the same damper and airspring that comes in the Lyrik Ultimate and Pike Ultimate.
Both of these forks use a RockShox DebonAir air spring which makes the fork feel super supple due to the large negative air chamber volume. The newest version of the DebonAir air spring has a totally redesigned seal head which has less stiction than the previous version. The airshaft itself is now hollow which creates an even larger negative air chamber volume which has even better small bump sensitivity than the previous version
So there’s the rundown on the popular RockShox forks, one of which you probably have. But why the heck should you upgrade??