Serpentine springs are also named as coupling springs and mainly made of 60Si2MnA and 50CrVA. The maximum spring thickness can be 20mm, and the maximum width can be 30mm.  Serpentine springs are supplied to users in sets (one coil is called as a set; sizes of user's serpentine spring will be tested when supplying goods; there are 1 piece for a sets, 2 pieces for a set, 4 pieces for a set and 6 pieces for a set etc.). Their scopes of torque range from 26 to 270000N.M, allowable radial displacement of two half shafts range from 0.5 to 3mm, axial displacement from 4 to 20mm, and angle displacement being 115'.