PREMIUM SOUND - This set of 2 Pro portable speakers features 40-percent larger neodymium drivers than the ULTRA, for crystal-clear sound. The stereo enclosure has 2x the acoustic air space and a 30-percent larger passive bass radiator for richer bass. IPX7 WATERPROOF DESIGN - Each waterproof speaker can be fully submerged up to 3-feet underwater for thirty minutes, so they are perfect for enjoying music in the shower or using as an outdoor speaker at the beach or by the pool.