I ordered a size 4 and it fit perfectly. I do not know what a UK 4 translates to in a US size, but it fits great. I love the Cobalt Blue. I purchased the entire set, I was happy they carry a 4, I have found many UK stores start with a size 6 which is way too big for me. Once you get the entire set on, it is beautiful, and I love the sheerness of it. Because it is so see through, it is a very sexy set. It shows through just enough to make it intriguing and a little teasing. I'm looking forward to wearing it. I am glad I purchased the entire set. It is also excellent quality and craftsman ship. It feels sturdy enough that it will last quite a while. I do not know what the sheer panels are made of, but they don't feel so fragile that they are liable to tear or rip too easily. But I'll still be gentle with it, nonetheless.