said by MrkFrnt:The yellow plastic is just sheathing, the actual gas line inside the yellow is metal and flexible.
Sheathing is only on the tracer wire buried with it.
The lines that I have had exposure to are 100% plastic.
In fact, if the tracer wire has been cut you can't even locate the lines and you must dig until you can find the tracer wire to be able to locate it.
(I am a former locator and gas was one of my utilities)
peace