Telescopic Lead Frames are manufactured for ease of installation in rough opening after wallboard is installed. Constructed from 16 gauge "JETCOAT" (HGDS) steel for rust resistance and paintable surface and fully lined with 1/16" lead lining. Adjusts for walls 4-1/4" (10.8cm) to 7" (17.8cm) thick. Fits into rough opening 1" larger than glass size. Refer to the Leaded Window & Frame Size Chart for standard sizes. Custom sizes also available. Note: Lead Glass, Acrylic and Frames sold separately.