The SOSS Invisible Spring Closer gives you a spring closer that is totally invisible from either side when the door is closed. When the door is open, you see only the hinge face and links. The closure rate is completely adjustable with an allen wrench after installation, and does not require removal of the spring closer. Installation can be either inside the door itself or inside the door jamb. Allow one spring closer for each 75 lbs. of door weight for all spring closers. The SOSS Invisible Spring Closer is ideally suited for all types of doors 1 3/8" thick or more. Recommended spacing is one half of the distance from the center of the door to the center of the top hinge.