PRO-FLEX gas piping is it durable for underground use?

According all I've read, " CSST for use in underground gas piping installations must be sleeved in suitable conduit, either electrical conduit or ABS. Larger diameter’s are necessary to pull the CSST thru the line, generally 3″ conduit is used. On the end of the line feeding your outdoor gas appliance, the end must be capped. Drilling a hole thru the cap and using a round CSST gas termination mount is the preferred method. On the opposite end, a “Tee” with a downturned elbow in the middle must be installed to allow the conduit to vent. CSST is much more expensive by the foot then poly underground gas piping, so it is only practical in shorter underground lengths, generally 20′ or less."

This pipe is designed for underground use. Remember though if you use this underground make sure it is far enough down that nothing will affect it. Usually you install at least 18 - 24 inches down. this protects the pipe from normal digging or applications of yard maintenance. When you do bring the pipe above ground it is necessary to encase the pipe in protective casing or attach any coming above ground in Black cast iron piping.