A:
It depends on when your SBE2 was made--it was manufactured in both sizes.
The early SBE2's use the standard Benelli tube.
Then they switched to Crio for the SBE2--most SBE2's you see will be in this configuration. If you have this version, you want the Crio Plus tube.
So you need to know which SBE2 you have (call Benelli with your serial number if you're not sure), then buy accordingly.