I originally used 1/4" lines for gas and had problems with leaking, a perpetual pain in the rear. Now I use 3/16" beer line on 1/4" barbs for both beer and gas. It's only a pain once. I just ordered new micromatic regulators for my new kegerator and the barb is 3/8". I was trying to figure out how to make that work until I realized I can just swap the shutoff valves and barbs from my old regulators onto the new ones.