Yep can confirm it is 20mm because Lou helped me fit it to my SE.
Um just becareful with Begi though.
Mine had the wrong thread for the sensor that screws into the side, so I had to pull the unit out again, get it re-threaded and install it again. Much easier to install though once you know how to do it. And the orginal unit is harder to get out than the begi one.
EDIT:
What came with mine: I bought mine 2nd hand, but unused and this is what it had.
Metal TBI pipe, 3 heavy duty proper hose clamps, length of 20mm tube, red rubber pipe to connect to TB.
You will need to pull out the sensor out of your original unit and install it into this unit. You will need a deep wall socket for this, which I didn't have, hence going to Lue's foe help. Beware of the thread, can't remember what its supposed to be, but mine was wrong. Also mine didn't have a hose clanp for the top little hose that plugs into the top of the unit, and it has quite a loose fit so you will need one.
Also may need some silcion grease or similar to put some of the pipes in.
Quickly went and had a look at mine and not sure if you will fit it onto a metal pipe, so i took a pic of where mine connects to the original rubber hose.
AT the bottom of the unit it is tapered in, with a little flange at the end so the hose clamp holds it to the intercooler out pipe.
The top just uses a round rubber pipe to connect the unit to the thottle body and the tbi, held with two eavy hose clamps. And mine hasn't move a single mili metre since installed in Februrary so it must have a pretty good grip. The stock one would move back about 5mm every 2-3months no matter how tight you made the crappy orignal hose clamp.
Hope this helps.
Also I found the install manual on line, which was crap. It has the old one, with the sensor connection to the left.
http://www.bellengineering.net/template ... 7ff7a5d4dcHave prices dropped on this thing, cause it looks chepaer than when I got it a couple of months ago.
Also noticed they now sell ones for 25mm BOV's as well as the standard 20mm.