The most comfortable waist pack ever! Like wearing a piece of lightweight clothing. Breathable stretch mesh and featuring the new Max O2 Waist(TM) attachment system. Daily training essentials; half marathon to marathon with water stations. Details: New stretch mesh fabric belt for lower pack weight and huge cooling and breathability! New Soft touch perimeter edging with beautiful de-bossed logos for a polished look, and a nonrestrictive feel. Max O2 Waist(TM) attachment system with greater recoil for better range of movement. Now with Magnon Electrolyte Pocket(TM) Built-in clips for race bib attachment that tuck away when not in use. Longer zipper on main compartment to accommodate electronics. Multiple reflective details. Available in size Small, Medium, and Large. Fit: Unisex Color options: Grey/Black, Luminous Blue, Twilight Green Capacity: 46 c.i.; .75 L Waist: Small 25"-33" , Medium 29"-37" , Large 34"-43"