In the automotive aftermarket, there are 3 common size air lines: 1/4", 3/8", 1/2". The most commonly used size tends to be 1/4" because it is the easiest to rout through the vehicle. Some people like the car to move from one position to the next faster than 1/4" can do (based on the flow rate and air spring volume/pressure requirements) so they tend to choose 3/8". The crowd that likes 1/2" will choose that size because they want the body to spring up very quickly when a valve is activated. Installing 1/2" lines can be the equivalent of wrestling an anaconda…