Design characteristics：

With spiral grooves a pitch (two left,two right,180°apart),"8"groove on

Material：

Diercet harden steel：GCr15(52100) 42CrMo(4140) 45(1045)

Carburizing steel：20Cr(5120) 20CrMo(4118) 20CrNiMo(8620H)

Copper：ZCuZn24Al6Mn3Fe3 ZCuAl9Fe4Ni4Mn2

Spring steel：65Mn 50CrVA 60Si2MnA