The vial is made of MS-compatible polypropylene, which consists only of repeating hydrocarbon monomer units:
These polymers have no polar or ionizable groups so the polypropylene vials are hydrophobic.
A primary reason one might use these vials is to avoid undesirable properties of hydrophilic silanols on conventional borosilicate glass vials is their hydrophobicity. The silanolic groups of glass can bind with basic functional groups, especially with proteins, where they cause low recovery and quantitative accuracy issues. Therefore, these LCMS compatible vials represent a solution to this problem as they may be more inert in this respect.