What you have will do the job as they also help with expansion and vibration issues....
Read the description on this "flex" joint and they say that the bellows style creates turbulence.... and I'd agree. Whether it's critical for your application is a different issue.
3" versions.
http://www.treadstoneperformance.com...Coupler+Bellow
Vibrant does NOT carry flex bellows in 3"