Product Info Catalog Hardware Builders Hardware Springs Extension Spring, 1/2-In. OD x 8-1/2-In. Extension Spring, 1/2-In. OD x 8-1/2-In. Request a Quote UPC: 38594003138 SKU: 681700 Model Number: C-313 1/2" OD, Extension Spring, 8-1/2" Length, .047" Wire Diameter, 13.3" Maximum Deflection, 7.47 LB Maximum Safe Load, Bulk With UPC.