A:Â
The clasp is a small plastic item. You would take one strap at a time and clip them into the holder. After doing so, your straps will be securely in place, and the clasp sits in the middle of your back. This allows you to have a "racer back" bra. It is a much prettier and feminine look, than having your bra straps showing while wearing a racer back t-shirt or top.
I must say, the brief "description" about the racer back option, does not have anything to do with a "good fit in a cotton bra."
May I suggest? It would be a great idea for you to attend your nearest Sears store, get a proper fitting from their bra specialist, and ask her for a good fitting cotton bra. You will end up extremely happy with knowing your "true" size, AND, a great, comfortable feeling bra. GOOD LUCK!