I'm not sure of the crossover's OD, but you can call them at 1.800.635.9781 & ask Tony or Mark (the owner). As for fit & leaks, it takes alot of "elbow grease" to get the 2 pieces together. The 1st pipe goes quite a ways inside the 2nd pipe, so I would think the joint would be pretty much leak free. You can use a muffler or band clamp on it just to make sure it seals nicely. Thanks.