Andersen Perma-Shield Double-Hung Window Narroline Counter Balancer - L12 / 1827Andersen Window Perma Shield Narroline Counter Balancer, # L12 1827 Balancer maintains the position of the window sash They are found above the upper sash in the head jamb, and are located on each side of the window This balancer is used on the right hand side of the window as viewed from the exterior of the window NOTE: If not sure which one you need, please contact us with the following information: 1. The Logo from the glass 2. The Width & Height