Heck No. Lol. 5/8". He had a 3/8" line on his compressor at home just to show me that the horn worked.
I run them at 150. I have the regulator set at about 154psi. But i mean there is some loss between it and that horns. They sound no different now than they did when I put them on. Well I take that back, they are louder now that the 1 bell isnt covered.
Look here, you can see that my 1 bell is tucked inside the bumper. I mean literally TUCKED in there. So before I removed that plastic insert, The 1 bell wasnt sounding at ALL.