I have two extruded circles (cylinders, each has a different radius, I'd like the centers lined up) that I'd like to mate in SW2006. I am able to line the planes up but I do not get a concentric mating option (it is greyed out). I've tryed to insert reference geometry but that does not show up in the assembly (I made points in the centers of the circles; once in a great while I am able to select one of the points, but I have not yet been able to select both and this does not seem to be a repeatable process as most of the time I am unable to select either points). Any suggestions? Thanks, David.