Thanks for replies. FWIW, I can reproduce at will by starting with the just the attached joined surface and then drawing a cylinder within the surface followed by alternating tapered and regular extrudes.
Hi Sven, yes it looks like the tapered extrusion surfaces can get pretty dense. If you need to do a sequence of several in a row you may be better off instead putting in circles and then using Construct > Loft > "Loft style = Straight".
