The AVS was before the UFS. Hopefully someone (Zor?
) will correct any errors but I believe the AFS was the first feed system which was for a 510 connection and the AFS would fit most any 510 mod. The AVSv2 was made of aluminum with a native internal 901 connector. Later production runs had switched to a native 510 internal connector and a nickel plated finish over the aluminum.
Many AVSv2 are still in active use (I use one daily) and the connector is modular meaning you can get the original 901 connector for it as the threads are interchangeable. The AVS utilizes the air control feature of the GGTS. The AFSv3 is essentially an AVSv2 with a module that allows its use on many 510 connector mods.
The latest feed system, The UFS features a native 510 internal connector and is constructed of primarily Stainless Steel with a plated brass base. In addition to air flow, it also utilizes a juice flow control. It also has the tank window and with the addition of the UFS top cap replacement (replaces the UFS mouthpiece basically), one can use almost any length atty or carto and your drip tip/mouth piece of choice.
While the AVSv2 is a great system, the UFS (or AVSv3) has more features and is constructed of a stronger material though somewhat heavier. The UFS is in perpetual demand and many if not most users consider it to be the state of the art of the GG feed systems. As good as the AVS is, it can still be found for a relatively decent price and condition.
