Tube Style pads are sewn closed at the bottom. For installation they slide onto the crossbar from an open end. For Aerodynamic style crossbars on standard racks. Typical 2.75″x.75″ (Thule Aero Bar) (Yakima Core Bar) (Yakima Jet Stream). 600 denier solution dyed polyester fabric. Very good resistance to UV effects. Aero size will fit most oval factory installed racks. Sold in pairs, packaged in poly bag with header. Made in USA.