ValueRays 2-Piece Set: USB Heated Slippers & One "3" Three Port 5V 3.1A Heavy Duty USB Adapter, (SMALL/MEDIUM) ValueRays 2-Piece Set: One Pair of USB Heated Slippers & One "3" Three Port USB Heavy Duty Adapter Heated Slipper Approx Sole Measurements: SMALL-MEDIUM: 11" L x 4" W; LARGE-XLARGE: 13" L x 5" W USB 5V Carbon Fiber Heating Element. Infrared Heat. Plugs into a USB port for heat. Gets warm, not hot. Heavy Duty 3 Port USB Adpater: 110-240V Output:5V=3.1A Requires 2 USB Ports or USB Adapters. Great for sitting at the computer or watching TV using a USB adapter on a power strip. Easy Disconnect Switch on 65" USB Cords. Each slipper has its own heat control switch. Cord color may vary.