This is a pack of 100 nickel plated 2-piece brass eyelets / grommets with an internal diameter of 9mm (3/8"). As the base metal is brass, these will never rust!
They are used to reinforce holes in lightweight leathers and fabrics.
The central tube is 5mm long, making these eyelets suitable for leathers of up to 3.5mm thick.
These eyelets are fitted with the Ivan 9mm (3/8") eyelet tool, found below in related items.