These replacement bubble tanks are perfect for increasing the capacity and look of some of the most popular older 22mm atty's such as the Subtank Mini clone (2ml version), Goblin Mini, Dotmod Petri RTA, Smok TFV4 Mini (rba version) as well as today's popular 22mm attys such as the Smok TFV8 Baby Beast (non rba and non EU version) and of course the Eleaf Melo 3 Nano. I managed to fit 3.7ml of e-liquid in these glass tanks. The price is excellent for five glass tanks. I have ordered more.