The Jacoby Black that came with the Mcdermott cue I just picked up fits nearly perfect and measures .860 at the widest and .857 at the narrowest points. It is perfectly flush except for a tiny over size at what I assume is the widest point. but then again these are very small variances and who knows if the McDermott joint is as close to round as the shaft is. The shaft is easy to measure unlike the butt side due to the direction of the taper. its easier to measure the widest part than the narrowest part. I measured a piece of paper from my sticky note pad at .004