1/4" (6mm). Mounts to the rocker box and adds a visual pressure check to your suspension system. Works with all air suspension systems. Allows quick and precise adjustments without guessing. Includes a white face 1.5" 160psi air pressure gauge, one T fitting and one elbow pressure line fitting, for a 6mm (1/4") pressure line, and a steel gloss black powder coated rocker cover bracket.

Fits: > 99-17 Twin Cam (NU)