They are the very same Polypro tanks from Valley View Vapors. The tube material is made from polypropylene, so they would be safe for use with all flavors of
e-liquid. They also use a
juice fill hole which some people believe is a benefit; I tend to loose small parts and would end up losing the screw for the fill hole, then the tank is useless. These tanks also use a rubber grommet instead of traditional end caps, which can be pretty difficult to work with when changing cartomizers.
Would not be close to being one of my first picks in a tank, but there are a lot of vapors who like these.