Available in Sterling Silver Size Reference: 17mm is the size of a US dime 21mm is the size of a US nickel 24mm is the size of a US quarter Saint Christopher Keychain can be engraved with a personalized message on the reverse side Available in Sterling Silver . Medal in two sizes: 3/4 Inch x 3/4 Inch (Size of a Nickel) 1 Inch x 1 Inch (Size of a Quarter) Custom Sized Available Upon Request. This Saint Christopher is the most popular saint worn by travelers.