The RS4 has excellent sound quality, much better than the traditional majority of players. It comes with 2 sizes of terminals (for outdoor use or for use under water) as the device is waterproof to a depth of 1.50m. The RS4 is not afraid to sweat, chlorinated water, sea water, it is solid and submersible. This is the perfect companion for jogging, hiking, biking, the gym, swimming, surfing and many other sports and activities.