The GS-Air, the GS-Air M, the GS-Air Ms and the GS-Tank are all clear
tanks made by eleaf/ismoka. They are inexpensive, reliable (long coil life), and they don't leak or gurgle. Those who try them often prefer them to many of the better known Kanger and Aspire
tanks.
Many of the GS-Air (all four varieties) users seem happy with the eleaf iStick 30w mod.
I have used that mod with all four GS
tanks for a few months and like them. I just got a Heatvape Defender 50w mod with a replaceable battery. That, too, works well with these tanks.