Shape-retaining thinstrap muscleback swimsuit for lessons and holiday fun. Stylish and comfortable, our Thinstrap Muscleback swimsuit features a pink 'Boom' logo. A great choice for swim training, lessons and active holidays, it's made from our soft-touch, shape-retaining Endurance®10 fabric. The thin strap muscleback design makes it ideal for longer training sessions, as it offers flexibility and freedom of movement.