I use the B2-FABF (F without the strap boses, N with) and love it. Recently I switched to the AS system which is without a doubt one of the best things I ever did. My B2-FABF lives on my BR strap and I have AS plates on my bodies and 70-200 collar. I can rapidly switch between strap and tripod. Unlike the photo on RRS's site, I orient the knob on the B2-FABF so it is towards the front of my body. Pick one up you will love it. I'd get the "F" version unless you plan to use the strap bosses.