If you are getting the charm by itself, I recommend a larger jump ring, so you can slip it on your chain. If you prefer a smaller jump ring and know how to open and close it to suit your purposes, let me know and I can use a small jump ring instead. For reference, the second picture shows the charms on my finger, with the "s" charm on the right using the larger jump ring, and the "M" charm on the left with the smaller jump ring. Default will be a larger jump ring, unless requested otherwise!
Thanks for stopping by CYC Jewelry! Don't hesitate to contact me with any questions.