This spring hinge is recommended for standard weight, medium frequency doors in place of door closers in apartments, hotels, motels, office buildings, etc. Spring hinges are an alternative to door closing devices. Generally two hinges on the door must be spring hinges to provide adequate closing force. NFPA requires a minimum of two (2) spring hinges on labeled doors. For maximum performance it is recommended to use all spring hinges on the door. This non-handed spring hinge series is adjustable and tension can be added or reduced by means of a hex key that is provided. Sold in packs of 3.