If you do not already know your ring size, fear not, this part is simple.
There is a printable size guide on the kit product page, which when printed, can be used as a reference point against existing rings (lay on top of the outlined sizes).
You could alternatively measure the circumference of your finger (in mm), and google the ring size conversion.
A final option when purchasing a kit (this would work most effectively when gifting the kit), would be to select an ‘unsized’ wax. You can actually size the wax yourself, using the sandpaper inside the kit. For guidance on how to do this, see our wax re-sizing tutorial; https://www.experiencecast.com/the-makers-table/#true