4200U Features: -Helps relieve neck pain and tension.-Helps reduce the effects of compressed and degenerative discs.-Helps relieve tension headaches.-Helps relieve pinched nerves.-Promotes circulation.-Promotes good posture.-Soothing stretching of the neck and shoulder muscles.-Recommend use the Neck Comforter about 2-3 times a day for at least 20 minutes each time.-No harmful side effects.