Making exhaust. Midpipe diameter 45mm?

[clucas]

I'm getting ready to slap together an exhaust for my bike. It only came with the manifold up to where the pipes meet. Is there a guide on the forum for this project? I have a pipe bender, welder and am planning on slapping it together on Friday. I'm supposed to be choosing a muffler from a friend in a few days, what's too big or too small?