Measuring a bicycle chain's pitch can be used to identify chain wear and flag the need for a replacement chain and/or cogs and chainrings. Bicycle Chains: Length, Width, What's Best to Buy etc.
An industrial, or scaffold, piercing is made up of two holes that are connected by a single piece of jewelry (usually a long barbell). An industrial piercing is commonly made through the cartilage on the upper ear, with one hole close to the head and the other further down on the outer rim. Two or more industrials on one ear is sometimes referred to as an ear cage.
Body Piercing. Most stainless steels contain deliberate additions of nickel. These steels cannot be considered for 'post assemblies' to meet the 0.05% maximum nickel level. Some attempts have been made to make ferritic or manganese / nitrogen based austenitic stainless steels with very low nickel levels.