The CRL/Jackson 21201 Series Overhead Concealed Closer with "U" Offset Slide-Arm Hardware Package consists of a Closer mechanism, which depending on the selected spring size and function, is suitable for a range of doors from 30" to 48"(762 to 1219 mm) wide. The Closer is packaged complete with Cat. No. 201387 Mounting Clips, 20942 Offset Arm Package, 20368 Slide Channel, and complete installation instructions. The Closer has dual independent valves for closing operation (one valve for closing, one valve for latching). 90 and 105 Degree, Hold-Open and Non Hold-Open models are available. Closers fit into standard 1-3/4" x 4"(or larger) header extrusions.