Tom,
I don't know what, if any, are the differences between a F3CB and a F3C funnel. I just was at the Mr. Funnel web page and they list the models differently yet: F1, F3, F8...so maybe they are simply revising their part number system.
Now we know the F3 size funnel is larger than the smaller F1 size funnel. But what hasn't been mentioned yet is that the F3 funnel has the filter raised above the bottom of the funnel so you always have an ounce or two of fuel left over in the funnel each time you use it. This design allows water and debris to collect in the residual sump area at the bottom of the funnel without obstructing the filter. But this means you must "dump the sump" after each use. The smaller F1 funnel does not have a sump area.
This also means, after you've transferred your fuel, IF you are not careful, you could hastily pick up the funnel and the fuel left in the funnel sump can slosh around - ending up on you and/or the ground/floor, making a mess of things if on you or if you are in an enclosed area.
What I've done in the past (typically when it's convenient for me- such as when I'm on pavement, in my shed, etc.) I use a small covered can that I can pour the ounce or two of fuel trapped in the sump reservoir. Personally, I like this design, because I can see if I had any debris in my fuel. Which means of course the funnel is doing what I intended for it to do - protect whatever I'm fueling from getting fed crappy fuel. Once the 'catch can' has enough fuel in it, I can simply run it through the funnel and start over collecting the residual sump fuel. :2cents:
Here are some more good points from Mr Funnel's web site:
FAQ
BarnieTrk