SID SL Ultimate 29in Boost Fork. The SID SL Ultimate is RockShox's lightest suspension fork, and is what we throw on our featherweight XC race bikes. RockShox went above and beyond to shed every possible gram, from hollowed magnesium lowers to a smaller bladder and damping system. Performance has improved over the previous generation SID to better handle small bumps and big impacts. The SID SL Ultimate comes slippery out of the box, and its Charger Race Day Damper is paired with a DebonAir spring to keep our tires planted to the ground as we charge through rocks and roots.More links or text can go here.