National Hardware V521 3.5" Spring Hinge Brass Steel 30 lb 3.5x3.5x0.125 in The National Hardware V521 spring hinge delivers reliable self-closing action for residential and light-commercial doors up to 3 ft x 7 ft and 30 lb in weight. Constructed from cold-rolled steel with a decorative brass finish and baked-on lacquer coating, it resists tarnish under normal indoor conditions while offering robust performance. Designed to fit standard 3.5-inch hinge cutouts with 1/4-inch radius corners, this surface-mount hinge features six pre-drilled screw holes (three per leaf) and includes all necessary mounting hardware. The spring tension and closing speed are fully adjustable using the included wrench, allowing customization for smooth, quiet operation in basements, garages, kitchens, and powder rooms. Features - Self-closing spring mechanism automatically returns door to closed position - Adjustable closing speed and spring tension for tailored door operation - Made from cold-rolled steel for strength and durability - Brass-plated finish with baked-on lacquer for added protection - Fits standard 3.5 in hinge cutouts with 1/4 in radius corners - Six mounting holes (3 per leaf) ensure secure installation - Supports doors up to 30 lb and 3 ft x 7 ft in size - Includes installation hardware and adjustment wrench - Suitable for interior residential and commercial applications - Compatible with fire-rated door assemblies when installed per code Specifications - Brand Name: National Hardware - Model Name: National Hardware V521 - Part Number: N185-199 - Product Type: Spring Hinge - Hinge Type: Surface Mount - Material: Steel - Finish: Brass - Finish Family: Brass - Length: 3.5 in - Width: 3.5 in - Thickness: 0.125 in (approx.) - Corner Radius: 0.25 in - Pin Type: Fixed - Number of Mounting Holes: 6 (3 per leaf) - Self-Closing: Yes - Spring Return: Yes - Adjustable: Yes - Weight Capacity: 30 lb - Suitable For: Hinge Cutout Doors, Fire Doors (up to 3x7 ft) - Application Environment: Indoor (Basement, Garage, Kitchen, Powder Room) - Item Weight: 0.70 lb - Packaging Type: Carded - Country of Origin: China - UPC: Not provided - Global Trade Identification Number: Not provided - Manufacturer: National Hardware Product Application This spring hinge is used by contractors, facility managers, and DIYers to ensure interior doors close reliably without manual intervention?critical for fire safety, privacy, and energy efficiency. Commonly installed on basement entry doors, utility room doors, and powder room doors in homes, it is also suitable for light-commercial applications like office partitions or storage closets. The adjustable tension allows fine-tuning for heavy solid-core doors or lighter hollow-core models, while the brass finish coordinates with standard interior hardware. Its compatibility with fire-rated doors (when installed per local code) makes it a practical choice for code-compliant retrofits where automatic closure is required. Designed for easy integration into new builds or replacements, it delivers dependable, maintenance-free operation in dry indoor environments.