Cold air intake question

I’m getting a welder to weld me up a custom stainless steel cold air intake and i was wondering what size air filter fits in the space below the air box?

there is quite a lot of room under there if u make it. sorry i dont have a filter size or anything but i do know there is plenty of room for a larger sized one especially if your making this custom

not too big if your talking about where the bottom of the airbox is…cuz i had mine located to there to be a true cold air intake…but…why would you have a welder make you one? you can make one out of tubing cheaper…like pvc piping used in bathrooms…the white plastic piping…otherwise if your talking about the top airbox probably like 8"…it matters how long the intake you are having made is…& what angle it is left at

I work at a company that sells stainless and this welder used to work there so he was going to weld it for beer and the stainless i can get cheap. So i fiquired what the hell