National Mfg. N185-199 V521 3-1/2 Inch Commercial Brass Adjustable Full Mortise Spring Hinge 3-1/2 Inch Brass Adjustable Spring Hinge, 1/4" Round Corner Designed For Hanging Self Closing Doors In Basements, Stairways, Garages & Entrances Can Be Used In Residential, Commercial & Apartment Buildings Closing Speed Is Adjustable Fits Standard Hinge Cutout, 1 Per Pack