If you have a brass or copper mech mod, then this top is for you. I purchased both of these as collector pieces but I tried them out. They work very well. The airflow in each cap is different and is unique for each type of cap. The airflow is not adjustable. If I had a con, this would be it. I like a little bit of a restricted airflow. These caps are not restricted. Other than that, these are great caps and if you have the dead rabbit, this should be in your stash of vape gear. Good luck and happy vaping.