D.O.T. tubing is required to meet standards defined by SAE J844 which requires nylon tubing. This standard also defines Type A and Type B tubing. Type A is 5/16“ OD or less which is what Freelin-Wade produces which are for instrumentation and pneumatic accessories connected to the air brake system. Sizes above 5/16“ are Type B tubing which requires a braid inside the tubing. This process requires machinery which Freelin-Wade doesn't currently support.