641 Adafruit Industries Conductive Thread, 3 Ply, 18M

This thread is 3 ply, thicker than every day polyester or cotton thread but still thin enough to be sewn by hand in medium-eye needles. This may be sew-able by a sewing machine that can handle 'heavy' thread. Because it is strong and smooth, its ideal for any wearable/e-textile project. It also has fairly low resistivity, 10 ohms per foot so you can use it to drive LEDs and other electronic components that use under ~100mA.

• Measures 0.25mm thick
• 3 ply thread
• 0.83 ohm per inch