A flexible gas line is an improvement over the old iron pipes that used to supply gas to stoves, furnaces, gas fireplaces and other appliances. Advantages to the newer lines include a decrease in necessary labor and the ability to add future lines fairly easily.
The key difference between flexible gas lines and their older counterparts is their material. Rather than heavy iron, flexible gas lines are made from corrugated stainless steel tubing (CSST). This has proven to be a safe and efficient alternative, and has been authorized by all state and local building codes as it has grown more popular with builders in recent years.
Flexible gas lines made of CCST don't require the labor-intensive cutting and threading iron pipes need. Instead, they're installed with much the same method used for electrical lines. They're laid out between two connectors, then cut to the needed length. These gas lines also remove the need for T-connections to change directions. The CSST can simply be bent as necessary. This flexibility has been shown to reduce the frequency and number of gas leaks, making it a safer alternative to iron pipes.