EZ Bracelet Sizer

Is this made of paper or vinyl?

If I'm using this tool to see if a bracelet measuring 7 1/2 inches will fit a 7 inch wrist, should the bracelet sit at the 7 1/2 mark or 7 mark?

If I want a 7 inch bracelet, does the bracelet sit on the 7 or the line above or below it.

How accurate is this? I see such mixed reviews!