The Brain is the mastermind behind Specialized's ultra-efficient suspension designs. It automatically turns the suspension "on" and "off" almost instantaneously to always provide the perfect ride. It consists of an inertia valve mounted inside a near-vertical cylinder near the rear axle. The inertia valve controls the shock's ability to compress; the resulting system responds to terrain input (bumps and dips), but not to rider input (pedaling). Forces from the ground activate the inertia valve inside the Brain, which opens and allows the shock to absorb bumps. All Brains also feature Brain Fade technology, which by using the blue dial on top of the Brain cylinder, you can control the breakaway threshold of the inertia valve in your Brain from ultra rigid and efficient to super plush and active and anywhere in between. So you can set up your bike to climb and sprint like a hardtail and still absorb bumps for maximum control over rough terrain; the ideal combination for parlaying all your hard efforts into off-road speed.