Patented Body Geometry design is lab-tested to assure blood flow to sensitive arteries. FACT carbon fiber shell is flex-tuned for support and ride compliance. Ultra-light, strong, and oversized FACT carbon rails. Level 2 padding: Medium density foam for bike feel with additional cushioning. Size 143mm / Weight 134g. Size 155mm / Weight 137g. NOTE: Oversized 7x9mm carbon rails are not compatible with seatposts equipped with side-load clamp mechanisms for 7mm round rails.