I got this adapter last Nov when I bought my MB20 setup. It has never been used and just sits in the MB case. I got it to mount the MB onto ENG rental cameras, when they don't come with a LWS 15mm rod mount. However, since I bought the thing, I haven't ever had to pull it out of the case. Also have 95mm and 85mm step down rings, which are the most common B4 lens OD sizes.
Gear lives in Costa Mesa, CA. PM me if interested.