The Luftkappe from Vorsprung Suspension increases negative air volume in air spring forks.  This greatly improves the two main issues with air springs: a high starting preload and a weak mid-stroke.  The extra negative volume lowers starting preload to zero, creating a pneumatic top-out effect.  The reduced initial spring rate allows higher air pressure for better mid stroke support along with improved small bump sensitivity.

Compatibility:
Fox 36 Evol 2018+:
Evol air system only.  Does not work with TALAS or FLOAT air spring systems.
Heavy duty F36 forks (E bike etc) have F34 internals and thicker tube walls..  Check volume spacers, green is 34mm internals, orange is 36mm internals.
Max 3 tokens due to reduced internal clearance.  Suggest tuning starts with 1 token.
SD Components DVC compatability is yet to be determined.
MRP Ramp Control compatability is yet to be determined.