NEW STYLES – WHISTLE V2. BLACK SPECKLE TEFLON OR WHITE TEFLON. STAINLESS STEEL BASE. Swappable Airflow Bores. Bore dimensions: 4.6 mm (without drip tip), 4.5mm, 3.5mm, 2.5mm, 1.5mm. Threaded works with Billet Box. 510 model can be used on any mod that takes a normal 510 drip tip.