It involves the melting of your raw material using oxyhydrogen flame as well as crystallisation of your melted droplets to kind a cylinder. Graded 9 about the Mohs-hardness scale (graded 1-10), the ensuing sapphire crystals are practically scratch-evidence and very tough, guaranteeing an unhindered eyesight at all times. Chrome steel https://www.watchesworld.com/top-10-dive-watches/