Its steel 3/8" fuel line. Used a 37° single flare. I didnt read that far in the instructions, however I think its pre set to 180° so it just loops back until it hits set temp, then goes through the cooler. The extra cost mounting bracket from Derale looked cheezy so I made my own that's much beefier. Used countersink screws where it tucks under the framerail lip. I mocked it up with 90° AN fittings near the K frame, ended up needing 120° AN fittings to get the lines away from the strut rod end. Works out good that way.