The piston failed a little after 2 yrs, and because of the design of the chair its almost impossible to replace.

the pneumatic piston tends to "leak down" sometimes rapidly sometimes it takes several hours

I gave it 4 stars, the only knock is the up/down piston is a bit noisy and sometimes not smooth feeling....

After having to return a brand new chair purchased from a 'superstore' chain online for a defective piston ( a completely different chair/brand) I must say I am pleasantly impressed by this chair