I completely agree with Kaboom. The BBS I is really small. The BBS II is likely a better fit for a 3wt. But if your 3wt is very small and light, the BBS I might be the option to go with.
I would check out the I & II side by side, and on your rod if possible.

The BBS reels are really a good value for the money. Very solidly made and a good drag system. The only thing that I do not care about them is that you really can't palm the reel very well. I like to reel in excess line by spinning the spool quickly with the side of my hand....and I can't do that with the BBS. But that being said, I own about a half dozen BBS reels and probably close to a dozen spare spools.

One nice thing about the BBS I is that it has a real drag on it. A lot of reels that size may not have one. The Bass Pro's White River Classic Ultra Light Fly Reel costs $100 and it just has a click pawl that offers no drag adjustment.

There's my 2 cents.....go check out the BBS I & II side by side if you can.

Brian