Tubing for cross members...

Just wondering what people are using for tubing for there cross members..
size and thickness...
thanks-

do you want round tubing or regular square/rectangular??? and will it be a structural( ie tranny , or 4 link ) crossmember, or just a frame support. It makes a difference. But for sure stay with .188 wall( 3/16 ).

Mines .250 wall. stupid thick.