... .springs for doors 4.professional work on cutting rolling shutter roll-up door spring A high-carbon steel that ... 5 mmWidth range: 8 ~ 650 mmHigh Hardness: Max. Rockwell-C 55 (HRB120, HV555)Standard/quality: DC01, DC03, DC04, DC05, DC06 ... Hardness as per client’s requestForms: Coils, Sheets, stripsApplications: roller shutter, rolling shutter springRaw Material: Baosteel CK67,SAE1065,CS70I.D. Coil: < 20 ...