Snake 40cm Chain width: Approximately 1.5mm Surgical Stainless Steel 316L What is Stainless Steel? A compound word of "stain" (to get dirty, to rust) + "less" (not). Literally meaning "difficult to rust" and "difficult to ionize." An alloy of iron, nickel, cobalt, etc. Although it contains metals that are likely to cause metal allergies, it is formulated with improvements to make them rust-resistant, and is attracting attention as a metal that is unlikely to cause allergies. It does not discolor in air and is hard and scratch-resistant, so you can use it with peace of mind.