The IBB convertible strap bra is a wire-free style with triangle-shaped contoured cups and a narrow band. It closes in back with a single row of hooks (like the classic Itty Bitty Signature Bra). The straps are detachable and can be worn cross-back, halter-style or classic.
The description of this bra on the IBB website does not mention the fact that it is a wire-free style. I would have preferred an underwire, because with the narrow band and only one row of hooks in back, there isn’t much support.
If you’re between band sizes, definitely order the smaller size — otherwise it will ride up (a common problem with wire-free bras). Sizes come in Extra Small (32), Small (34), Medium (36), and Large (38). Cup sizes are all AA/A; I would not recommend this bra for B cups.