Sirrus X 2.0 Step-ThroughThe Specialized Sirrus X 2. 0 provides the smoothest ride in its class. With bigger, confidence inspiring tires, a slightly more upright riding position, and a super intuitive one by drivetrain. RIDER FIRST ENGINEERED: Like all Specialized performance bikes, the geometry of each frame is uniquely crafted. This means that for every frame, each tube size is specifically selected to achieve the optimal balance of rigidity, weight, and responsiveness to