Profile Design ATTK XL Top Tube Storage. The Extra Large ATTK top tube storage allows you to fit even more of your preferred nutrition in a sleek package that tucks out of the wind behind the stem. ATTK XL is designed to improve aerodynamics while offering a streamlined storage solution. The uniquely designed shell allows cables to route straight through to the top tub. Mounting is simple and can mount onto most bike by using a direct top tube braze-ons on compatible bikes or using the supplied FPS Straps.