The Innokin Axiom tank is fully TPD compliant and features a 2ml capacity tank, top-filling design and powerful sub-ohm capable coils. Innokin Axiom M21 Tank. Designed By Innokin in California, the Axiom is an Ultra-Compact 22mm tank with 3.5ml capacity and advanced integrated top fill design.Crafted with top quality Stainless Steel & Pyrex Glass, the Triple AFC Intake directs maximum focused airflow to the dual horizontal coils for amazingly intense flavors and deep, full clouds.