As long as the narrow part penetrates the bar, all's well.  The conical hilt of the nose will meet the inner lip of the bar at different depths depending on the inside diameter of the particular bar.  In the new Smooth City tm weight series, you can make up the difference with the internal shims supplied with the kit.  On the other hand, 2 1/2" of depth is required inside the bar to seat the assembly properly.  If there is something in there that is shallower than that, and it does not have screw threads, my stuff won't fit.  If it has screw threads 8mm or narrower, you are looking at the wrong weight now.  Call us 763-234-7242, and we'll get it sorted out.