The Brain is the mastermind behind Specialized's ultra-efficient suspension designs. It automatically turns the suspension on and off almost instantaneously to provide the perfect ride. An inertia valve mounted inside a near-vertical cylinder near the rear axle controls the shock's ability to compress; the resulting system responds to terrain input (bumps and dips), but not to rider input (pedaling). All Brains also feature Brain Fade technology which allows you to control the breakaway threshold of the inertia valve. This turns your Brain from ultra rigid and efficient to super plush and active.