My mom gave me several of these 7 years ago and after so many years of daily wear they are just now starting to deteriorate.  My old ones are so worn I couldn't see the size, so I guessed and ordered a size 42.  I am a 38D, but I didn't want them to smash me flat like a sports bra so I sized up a little.  These fit perfectly!  They offer enough support that I can wear them in public without thinking about it, but they're comfortable enough that I sleep in them every night.  They're great for wearing under low-cut tops to show a little modesty or with wide-neck shirts to show off the cute thin straps you don't really get with most 38D bras.  I plan on ordering at least 1 more set if not 2 to replace the ones I've been hanging on to for 7 years.