BERLEI. Ultimate Performance Underwire Sports Crop has a support factor of 4 which will reduce breast bounce by upto 60%. This crop features seamfree, moulded cups that provide breathability and reduces chaffing. The J-Hook racer back clip and hook adjustaments allow for multiple shoulder strap options. It is also designed to hold a heart rate monitor and an MP3 player. This crop is ideal for those extreme high impact sports.