<center><img src="http://pictureposter.audiworld.com/8297/bell_mouth.jpg"></center><p>

I would love to be able to get more but due to physical constraints of the airbox lid I have to compromise. On an external application where size were no limit I'd like to have almost a 2:1 inlet flare to outlet I.D. ratio. Unlike your drawing however the best velocity stacks utilize a straight rather than fully radiused taper inside the flared inlet.

So what can it be? 1", 2",3"...?

cracking/splitting. I've never gone for max-stretch to test it. But if you are specifically seeking a MAF flange for a cone setup I've got a nifty trick on how to make one thats cheap, a beauty and very very slick.

and depending on length of tube used I could likely flare it to that diameter without any compromise or distortion of remaining unflared 3" tube.

<center><img src="http://pictureposter.audiworld.com/8297/bell_mouth_flange.jpg"></center><p>....purposes.

Which I will except but I like to see if my way pans out first.