For use in Fire Rated Applications
SOSS Invisible Hinge is ideally suited for most types of doors.
Totally invisible from either side when the door is closed.
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.
SOSS Invisible Hinges open a full 180 degrees and are a single action hinge.
Allow one spring closer for every 75 lbs of door weight
Recommended spacing for use of one spring closer is half of the distance from the center of the door to the center of the top hinge.
Wood screws are included. Machine screws are available for an additional charge.
Made of Alloy Steel
UL Rating: Can be used on hollow metal , sheet metal, tin clad, and steel composite swinging type fire doors and frames rated up to and including 3 hours. They can also be used on wood core doors and frames rated up to 20 minutes.
Additionally, they can be used on wood/plastic composite doors and frames constructed with Georgia Pacific FS 1 or FS 2 banding for a rating up to and including 90 minutes.
Use at least one fire-rated hinge for every 20 in. of door height or portion thereof, or one hinge for every 60 lbs. or fraction thereof, whichever calculation demand more hinges.
Per Package: 1/Box=1 Each
Per Carton: 1 Each
Weight per Carton: 2.5 lbs