Ring Sizer with magnifier. 
These are US sizes
If purchased alone, this will be shipped in a standard envelope with a stamp. No tracking info.  
This one is in-between the 2 ring band widths I use.  I have made sure these sizers are accurate to sizing tools I use. 
Tips. If you are a size 7 but having a ring made in the wider band, you'll go up 1/4 size.  For the smaller band you'll go down 1/4 size.  You can also message me for help on deciding your size.  
If the magnifier is between 2 sizes, then that is a half size.  Example: if it's between the 7 and 8 then your size is 7.5