The Eleaf GS-Air 2 improves upon the GS-Air. First included in the Eleaf iStick Basic Kit, the GS-Air 2, due to its success has been released as a stand alone tank. So grab a spare for your Kit or use  it with a different device altogether.  
 
     
Eleaf have made some significant changes with the release of the GS-Air 2, mainly the 'Thread Adjustable Air Inflow' of the original has been replaced with a much more user-friendly 'Air-Flow Control Ring', as can be seen on many other manufacturers tanks.