Most 1.5mm to 6.00mm crimp tools have one half of the crimptool that does the crimping and the other that makes it kinda look pretty at each end, if you know what I mean, which is ok except if you get it the wrong way round it can go look as though it has crimped, and be quite firm, but all you have crimped onto is the insulation. I always go for the ones that crimp on both sides of the tool so you get a double crimp affect on the lug or ferrule. Not such a pretty finish, but always certain to be crimped up nice and tight, but you will have to shop around the wholesalers.
good luck.