SUPERSEN GAS SPRING force as shown in the compression direction of the F3 and F4, and the stretching direction of the F2 and F1. F3=COMPRESSION FORCE PISTON ROD EXTENDED F4=COMPRESSION FORCE PISTON ROD RETRACTED F2=EXTENSION FORCE PISTON ROD RETRACTED F1=EXTENSION FORCE PISTON ROD EXTENDED FR=FRICTION FORCE = F3-F1 , F4-F2 SPRING RATE (X)=F2/F1 Generally , SUPERSEN GAS SPRING force referring to F1, is the GAS SPRING done before the maximum length of 10mm position measurement. In some cases, F3, F4, F2 also to be took into considerations according to users' needs.