Brake lines

[stevestang1966]

This is going to sound really stupid but I am having a hard time finding an answer. My 1990 Mustang rear hard brake line (not the hose) blew and I am going to get a replacement but with out taking it off the car I do not know what size it is. Does anybody know the outside diameter 5/16,3/16 etc?
Thanks

 

[BlackFox5.0]

www.discbrakesrus.com has a stainless steel replacement for around $30