I just open yg five pawn tank tuw build my new coil and i just looking foward to check it even more, and guest what.in the center pin hole there was something stuck.I think that why it felt heavy for me to take some puff. The thing that stuck in the center pin was the piece of drilled that being use to make the air flow.so for someone that use kayfun five pawn u better check it out for a better puff