Detailed Product Description Zigzag spring,nosag spring,sinuous spring,coil spring,sofa spring,seat spring,back spring belong to sofa part or sofa fittingspring feactures: Wire diameter: 3.0mm-4.3mm Pitch: 16mm-25mmArch Height: 40mm-55mm Process: All springs are with heat treatment and anti-rust treatment.Packing: in poly bag or carton The follow size is commonly used: (pitch:18,loop height:48)