The CRL DC54 Size 4 Surface Mount Door Closer is perfect for most commercial applications. The Size 4 spring is suitable for interior doors up to 48" (122 mm) and exterior doors up to 42" (107 mm). Applicable door weight should be between 143 and 187 lbs. (65 and 85 kg). The closer is supplied with an adjustable back check feature to protect the doors and hardware from damage due to wind or violent door swings in the opening cycle. Both the closing and latching speeds are independently adjustable and will satisfy your customer's requirements for smooth operating door control. All CRL Surface Mounted Closers are UL listed and warranted for ten years. A Parallel Arm Bracket and mounting hardware are included with each closer permitting universal installation for regular, top jamb or parallel arm applications. Optional accessories, such as Drop Plates and Hold Open Arms, are available for special installations.