DIY Styrofoam No Sewing Avalon Cornice 2-Piece Extension Kit 12 Inch Drop Our Bay Window Adapters and Corner Window Adapters make it super easy to accommodate those tough to measure angles. Also available in 9&quot; Drop and 15&quot; Drop. Assemble - Decorate - Hang - That&#39;s all there is to it! No Sewing! The styrofoam pieces are glued together using a low temperature glue gun. Use our cornice kit and extension kits to create a cornice up to 50&#39; in length.