Product Info Catalog Hardware Builders Hardware Springs Extension Spring, 5/8-In. OD x 8-1/2-In. Extension Spring, 5/8-In. OD x 8-1/2-In. Request a Quote UPC: 38594003213 SKU: 681742 Model Number: C-321 5/8" OD, Extension Spring, 8-1/2" Length, .062" Wire Diameter, 10.7" Maximum Deflection, 12.9 LB Maximum Safe Load, Bulk With UPC.