If you have purchased from a brick and mortar store, or ebay, or an online re-seller... chances are you have already used a fasttech product. I know for a fact the vape store close to me uses Protank II knockoffs from fastech. They are the ones with the tinted glass, they even color code the flavor types. But my local store wont sell the knock offs to the public, they just have them in the sample rigs for trying juice. They sell the real deal ( or a good counterfit ) at 50$ a piece!!!!
I go there for juice tasting, and occasionally a few coils... everything else I bought online, some from fasttech. The two things I wont skimp on are real name brand coils, and juice. Everything else can be copied and copied well.
When I browse around the brick and mortar store I look at what they have for sell, if I like it I order it online ( fasttech ) is cheapest. But I always buy at least one bottle of juice to show a little support...