It didn't fit me. Depending on the brand of bra, I'm either a 38F or 36G. Genie bra doesn't make that size. I even tried doubling up. I tried it on at Target. It came in a box of 2 for about $20. Genie bra gave me a uni-boob look, lol, no definition, no support. Maybe if you are taller and don't have a bigger cup than a DD, but I'm 5'2" and top-heavy.
I was fortunate to find Genie Bra at Wal-Mart and try it on. I didn't care for the fit and didn't buy it. See if you can find it at a department store instead of buying it online, so you can try it. What I didn't like was that it tended to bunch up and wrinkle on me. It was hard to get in and out of, and it was overpriced--especially if you have to purchase online and pay the outrageous shipping costs.
What I have always done with my bra is put a hair clip or Bobby pin in the back to attach the straps. I bet if you kept your eye out you could find something around the house or in product packaging that would do the same damnedest thing.