1.material:Sup7,Sup9,60Si2Mn,50CrV,50CrV4 2.thickness:from 6mm to 50mm 3.shot peening 4.hardness:375-444BHN 5.customized We can supply quality tapered parabolic leaf spring for trucks and trailers,applicable to the truck & trailer of MAN,VOLVO,BENZ,DAF,HOWO,HINO,ISUZU,MITSUBISHI,KAMAZ,GAZEL etc.