This model is a Safety Third key ring / key chain!
This keyring is 8.2cm wide, 2.4cm tall and is 6mm thick.
Keychains are designed with a 'channel' to allow for a 2.4mm (or smaller) ball chain to be looped through. Ball chain is available very cheap online in a variety of colours - we suggest cutting the ball chain to a length of approximately 15cm.