Floyd Blue has an excellent article on the BO/TMB planetary lineup here on AM.
I just want to relate a short but rewarding viewing session I had this morning. I used a 4mm BO/TMB with my Stellarvue 102/f7.75 doublet apo. I get 200x with this eyepiece, a perfect 50x/aperture. A 20.2 lunar day gave me a rilly good time
I resolved rimae Ariadaeus and Hyginus (always easy) and Hypatia and Sosigenes (I've been trying for that one many months now.) Treisnecker was disappointing with only part of one rille visible, but... Hadley gave me an usually good show with nearly all of it visible winding its way through the Appenines. I rounded up the rilles with Plinius and Sulpicius Gallus. I resolved Catina Davy Y about as good as I ever have, with the smallest craterlets nearly resolved. The mounds Arago A and B were very prominent and I could just make out the pit at the summit of one of them. The 4mm performs extremely well as a lunar eyepiece. No flaring or lateral color could be detected and as Floyd reported, very sharp at the edges too. I could have used an ND or polarizer filter, as the image was quite bright in the SV102ABV. I felt like the outer edges were closing in on me with no filter in place to reduce the light intensity, but I prefer viewing au natural.