Window Hinges/friction hinges are available in many types and sizes. Window Hinges may vary in style depending on type of hinge selected. Window hinges are sold in pairs as there are two window hinges required per one window. Be sure to select the proper stack height for your window hinges as explained in the product description. Also make sure you choose the correct length of window hinge to match the existing window hinge you are replacing as this is also key to a perfect fit as the window hinges are designed to carry the weight of the window.