Replacement negative spring. Adjusts the static ride height of the fork for desired travel settings. Stock negative springs will set travel to correct height at 90 psi. 

Compatible with Aion-Auron-Durolux series forks

Soft spring = riders using 60 psi or less air pressure. 

*Generally for riders of 150lbs or less

Firm Spring = riders using 105 psi or more air pressure

*Generally for riders of 200lbs+ or for very aggressive riders. 

Stock Spring Chart

air pressure	travel change
psi	mm
40	-31.9
45	-26.2
50	-20.5
55	-14.8
60	-9.1
65	-5.5
70	-4.4
75	-3.3
80	-2.2
85	-1.1
90	0.0
95	1.1
100	2.2
105	3.3
110	4.4
115	5.5