Maybe you got 20700 wraps instead of 21700 wraps? They'll fit, but not correctly. Too tight.oh. I tried to fit a 21700 into 18650 wrap, no go. so, it seems I got correct 21700 wraps. unless there is a batt size in between, idk .
but boy, the 21700 wrap is VERY TIGHT, think virgin. compared to the 18650 wraps, $.50 hooker.
http://vapingunderground.com/threads/wts-wtt-aspex-performance-coils.434798/