... blue tempered spring for rolling shutter 2.CK67,AISI 1065,1070,CS70 3.0.15~2.5mm*8~650mm 4.round, slit Blue ... Tempered spring steel strip for rolling shutter doorHeat treatment is ... or EK2, EK4Finishes: Nature, Polished bright, grey blue, polished blue, yellowEdge: Mill, Slit, Round, sheared/millTensile ... weight: < 6,000 lbs, 2727 kgs blue tempered spring for rolling shutter