I have been selling women's panties on ebay for 6 years. I currently have a  Ebay Store with a large variety of panties sorted by size categories or your favorite character.  I have learned that different manufactures use different way to state their size.  Some use words: small, medium, large.  Others use numbers, 5, 6, 7, 8, 9, 10, 12.  And yet other use clothing size 18/20, 22/24, 26/28, 30/30.  Here is a correlation that I have made for the different sizing.  Please note that these are general correlations and different manufactures sizes still may vary.

• Small - Size 5 - 3/4 or 5/6
• Medium - Size 6 - 7/8
• Large - Size 7 - 9/10 or 11/12
• XL - Size 8 - 1X - 14/16 or 18/20
• 2X - Size 9 - XXL - 22/24
• 3X - Size 10 - 26/28
• 4X - Size 12 - 30/32

So when you are searching for panties you may need to try searching for you size in different ways.