Make sure the strap and sides are wide as mine moved about and was very uncomfortable. I bought a few with a slim back and sides and these uncomfortable but looked pretty and didn't give me much support. I got another from Marks and Spencer and that's thankfully comfortable. I'd recommend trying lots on. Some were way too big in my usual bra size and others too small. I tried loads on by wonderbra, ultimo, gossard and Trumph. Try it on with the dress you intend to wear it with.