Black 1/8" ID (3.2mm) Nitrile (Buna N) Fuel and Smoke Tubing. 1/4" OD (6.4mm), 1/16" (1.6mm) Wall thickness.  Buna N is more flexible than the yellow Tygon and will not harden. 

Sold per foot.  For example If you want 6 feet of Tubing order a quantity of 6 and it will be 1 piece that is 6 feet long.