The Smashpot from Vorsprung Suspension replaces your entire forks air spring system (left leg internals) with a full length coil spring and externally adjustable hydraulic bottom out (HBO) system.
Coil springs offer performance that doesn't give a damn about temperature or altitude. They have great mid-stroke and incredible small bump compliance. The elimination of the air spring seals greatly reduces friction and the spring side now uses 100-110 cc of lubrication oil.
Yes it is heavier than air. Weight matters most when you're talking about it.
Fox 36 2015+:
M34 x 0.8 mm top-caps.
130-180 mm travel set internally with spacers
Riders approx 45-125 kg
Core components can be used in other compatible forks with new caps and feet.