Pete,
Brett's article on Heman's website says .259.  My mic says .256.
http://www.aeromaniacs.com/brett.htm

Would it be nosy to ask what plane you're putting it in?

Thanks for that Kim, I didn't realize Heman had that posted there...great site! Plane, probably a trainer, we have been getting some new folks interested in the sport up here and I thought it would be nice to have a plane for them to try. Clint, I'll take you up on that offer. Put one aside for me, I'll give you a call 'bout delivery. 

Thanks all, the only ones I have on hand are larger, for FP-40's and the like. 

Pete, depending on your intended use, further to Kim's comment, several people in Oz are having great success with the small venturi that used to come with the FP 35 and FP 40 on the LA 46.

There was an article in Stunt News some years ago by somebody who was enjoying success with FP 40s using the FP 20–25 venturi.

When Kim says 'It really sucks', I hope he means that there is a lot of suction and not the way the kids of today would be thinking when they say that.

I suspect that the FP 20—25 venturi is a little small for the 46 but a good candidate for slight opening up if you do not have any others to use.