I think that's called the Alpha because it's the first one and it sounds cool. It should be .455 in size, see proptop's post above.

I flew my .46NT 3 times last weekend on a Magic Extra. I used a TF 10-6 and 15% Cool Power. I didn't tach it. The needles were off. Both needles were too lean. I have reached the limiter on the high side needle. That's easy to get around though. Not as powerful as the 46FX but, close. The more I ran it the better it got. I didn't play with prop sizes or anything else. I'll let you know more after this weekend.