For the poly wire, we used the stainless steel #304A to make the poly wire, the stainless steel wire of the poly wire must be with super anti-rusted performance and good conductivity, so the wire standard or our poly wire: GB4240-2007，nickel content not less than 8%, chromium content not less than 15%, otherwise, the stainless steel wire of the poly wire will be easily rusted and with inferior conductivity. besides, the stainless steel wire of the poly wire must be hydride process (temper process), otherwise, the stainless steel wire will be easily bended.

the available stainless steel wire diameter of poly wire as following:

Φ0.16mm  stainless steel wire, normally replaced by Φ0.15mm
For Φ0.15mm, the tolerance is 0.005mm, that is Φ0.145~Φ0.155mm

Φ0.20mm stainless steel wire, the tolerance is 0.01mm, that is  Φ0.19mm~Φ0.21mm,

Φ0.40mm stainless steel, replaced by Φ0.35mm, Φ0.37mm

Φ0.38mm stainless steel wire, this is not available, normally replaced by Φ0.32mm