Front frame channel size

I'm trying to build a front bumper for my jeep and I want to use square tubing inside the frame rails does anyone know what size I should use

It's a 93 2 door

I believe I used 2x5 rect tubing on the inside on mine in the very front. Be warned though, you're not gunna get the tubing to slide very far into the rails. The DS has the inner sleeve thingy for the steering box bolts and the PS has a weldnut or two on the inside as well.

your better off with frame rail tie in plates than sleeving the inside of the unibody for the front.