Sennheiser is the acknowledged world leader in headphone-transducer technology. These CX 300 headphones are its first consumer ear-canal model. The CX 300 model is ideal for use with portable MP3, CD, MD, DVD players and many other portable devices with 3.5mm headphone sockets. Soft Silicone-Rubber Ear adapters in three different sizes are included to ensure a perfect fit, high wearing comfort and an excellent attenuation of ambient noise.