The Antares is 1 of fi'zi:k's 3 Spine Concept Mens Road Saddle shapes. Of these 3, the Antares shape is wide and slightly curved in profile.Antares R1 is for The Chameleon: Medium Spine.If you have an intermediate degree of spinal flexibility (approximately 90 degrees between your straight legs and your back when bending over as far as you can, keeping your legs straight a shoulders' width apart), you are a chameleon. Your degree of spinal flexibility helps you so far, before you need to rotate your pelvis slightly to achieve fully the performance position.You will benefit from the increased width and slight curvature of the Antares shape.Key Features:Shell: Carbon Thermoplastic Composite with Wing Flexfor freedom of thigh movementRail: fi'zi:k kium Cover: MicrotexThigh Glides: MicrotexIntegrated Clip System: YesLength: 275mmWidth: 142mm (regular) / 152mm (large)Weight: 200g (regular) / 205g (large)