Tank fuel lines

So apparently when manufacturers state tubing is fuel rated, they mean on the inside only. The fuel line inside my fuel cell had gotten rock hard and actually cracked, which allowed the pump to suck air instead of fuel. That's why my car started running all funny, to the point where it would barely run. Anyway, it turns out they make submersible fuel line, which is what you need inside of your fuel cell. Just a word of caution for those of you that have any flexible line inside of your fuel cell or tank.