Do not go by the manufacturer specified size. The size they give is for the entire watch and not the glass portion.
Measure the diameter of your watch face. Measure ONLY the glass part. This will be the size needed.
Order a size smaller than your measurement. If you measured 36.5mm you will need 36mm.
Still unsure? Use the contact page and email us your exact watch model number. We will email you back with the size required.