These are brand new 18k yellow gold seam rings, handmade to your measurements here in my workshop in the UK. The size of these rings is 1.2mm with your choice of internal diameter (select from the drop down).
These are made with gently rounded ends to allow easy insertion. To open you gently push at the join, pushing each end in different directions sideways (see the third photo to see this). If you pull them open (so pulling the ends away from each other on the parallel plane) you will be unlikely to get it into a completely round shape afterwards. To close you push the ends back into position the reverse of what you did to open it.
Quantity: 1 Ring