Steel disc material
ETFACE：Material: 65M with heat treatment, stronger and keep flat
OTHER:Material: 45# no heat treatment, less strong, easy to get broken
Springs material and life
ETFACE:Material: 55CrSi, no broken, life for at least 7 years for perfect performance
OTHER:Material: 65M,or 60Si2Mn, easy to get broken， working time less than 6 Months
Facing material
ETFACE:Material: Raybestos and upon to the requirement from customers , durable, feel comfortable when drive
OTHER:Material: Bad material, less life time
Hardness
ETFACE:The hardness for this parts is: HV500-600,with perfect heat treatment, the thickness of heat treatment is:0.2-0.4mm.
Strong enough to prevent the spring from coming out
OTHER:No heat treatment, result in the coming out of the spring
