You are talking about OPAL , right ? <| sep |> Cook bacon <| sep |> I just assumed on the engine and tf that I could adjust the airflow to my likingSee my Serpent Mini 25 mm and Limitless example above . To a degree what you say is true , but only to a degree . The chimney and chamber will have an effect on how restrictive the airflow can get . although wouldn ' t the V 3 be better ? The v 2 . 5 was actually released after the v 3 , due to complaints from people who missed certain aspects of the v 2 that were not in the v 3 . Check the reviews for the v 3 and compare them with the v 2 . 5 , you ' ll see the v 2 . 5 is more highly regarded than the v 3 . And just judging from pictures the v 3 has a wider chimney and larger chamber . You ' re much less likely to get any kind of restricted lung hit from the v 3 , which is why I mentioned the v 2 . 5 . The smaller chamber and narrower chimney means you ' re more likely to be able to achieve a more restricted lung hit .