here are pics,but as i said;it sits flush with 510 adapter but not with the outer ring, so it's not a tank 510pin length issue.View attachment 640547 View attachment 640549
Looks like the adapter is upside down. That taper in your second pic should be against the mod. If the other side of the adapter doesn't have grooves and is not tapered on the edges then you got a flawed adapter. Frankly though the groves are not needed anymore since tanks stopped using bottom airflow. Try flipping it over first. I'll post some pics in a bit to show you what I mean.