3.5 in. x 3.5 in. Satin Brass Steel Spring Hinge with 5/8 in. Radius (Set of 2)The Global Door Controls 3. 5 in. x 3. 5 in. satin brass steel hinges with 5 8 in. radius functions as a full mortise single acting spring hinges. Recommended for use where automatic self closing of a door is required. The 2 knuckled hinges is adjustable and the spring tension can be increased or decreased by using included adjusting tool. For maximum versatility use 2 hinges on required opening. Full spring tension may not be required on all hinges