But we can do some quick arithmetic. Define penis #1 as having girth G1, and length L1, same idea for penis #2. A bit of figgurin shows the volume of the erect penis is given as LG^2/4PI. Then it is easy to see that the volumetric ratio of the penii #1 vs #2 is given as (L1/L2) * (G1/G2)^2.
So in terms of length by girth, if your penis is 6" x 3.9", and the bgff's is 9" x 5.9", the volumetric ratio (with dude as the numerator cause he's in charge) figures to be a whopping 3.4. When (not if) the black guy is lovin your ex, IF he were to withdraw and let you have a turn, it would take 3.4 clones of your penis to restore ex gf's latest sensations.
To the original term of this entry, bbgffkr's penis has 3.4 times the cell count of your own penis cell count. And your ex is getting the pleasurable tug you shall never deliver without a prosthesis.