Think Tamiya made a mistake in the manual..... See post#2 for the order is o-ring > spacer > large spacer. Post#3 spacer BD10 > o-ring BD11 > larger spacer BD12. I follow the manual in post#2 and spend over 2 weeks try to get the shock smooth. (change o-ring, spacer, piston.......) After change to post#3 everything is working nicely and over 2 months now....