Use these headphones and earbuds as a spare or replacement set. They work in tandem with Xen to deliver VNS signals through your left ear.     Features Spare or replacement headphones and earbuds for use with Xen  Patented technology works in tandem with Xen to deliver VNS signals through your left ear Includes earbuds in sizes S, M, L, and XL   These headphones and earbuds can only be used with Xen  What’s in the box Xen Headphones  Xen Earbuds in sizes S, M, L, and XL Specs  Headphones + earbuds weight: 0.5 oz Transducer: Speaker driver Impedance: 16 +/-2.4 ohms Frequency response: 20-20,000 Hz Sensitivity: 94 +/-3 dB @1kHz, 1 mW