... spring parts),zigzag spring,sinuous spring,coil spring,sofa spring,seat spring,no sag spring. OKE clip knot (no sag spring parts), zigzag spring,no sag spring,sinuous spring,coil spring,zig zag spring,sofa spring,seat spring ... used: (pitch:18,loop height:48)(2) OKE clip knot (used with no sag spring) 1).high-tech plastic material 2).economical and ...