Newbie to the benjamin kratos

I wonder if i need to remove the brass screw on top to remove the bottle
IMG_8590.jpg
IMG_8590.jpg
 
There's a woketube i mean youtube vid on Benjamin kratos disassemble and parts. It shows the bottle removed but theres a somthing still in the neck of the bottle. But that part looks to have 2 flat spots to fit a wrench to maybe remove / unthread it from the bottle neck.. then you can maybe have a open neck to inspect the inside of the bottle. If theres a carbon mod tank im sure that has to be removed and installed on one as well ( youd think , right?)