The Sirrus X 4.0 offers an unparalleled combination of comfort, efficiency, and agile handling, excelling on asphalt, gravel, and any terrain in between. SMOOTH, COMFORTABLE, AND EFFICIENT: The Sirrus X is characterized by the calmest ride in its class. It features larger, confidence-inspiring tires, an upright riding position, and a super-intuitive single-speed drivetrain. RIDER-FIRST ENGINEERED™: At Specialized Bikes, each frame size and geometry is individually designed rather than just scaled down. Tube lengths and diameters are optimized for the best balance of stability, weight, and responsiveness for every size. The goal? No matter which frame size you ride, we ensure you experience the best ride feel in the world. AGILE: The low weight, exceptional pedaling efficiency, and steering precision come together to create a smooth, almost telepathic riding experience.