Hi i have 2 db drive wdx 2k 12" subs and tthe factory recomendations are 2.7 cu. Ft per sub. I have a box drawn up that is exactly that with 2 seperate chambers and as of right now its sealed in my drawning. But this is my first box build and i have no idea how to build a built in port but id like to use the plastic tube ports that you just drill a hole and drop in and i have no idea what size one i would need. I have done alot of research and i cant find anything. If anybody can help id really appreciate it.