VWR Collection flasks are vacuum gas plasma treated for consistent cell attachment and growth. Vented caps incorporate a 0.22 µm hydrophobic filter to allow gas exchange and minimise risk of contamination. Flasks are clear, virgin polystyrene. They are sterile and certified non-pyrogenic. The angled-neck design of these flasks offers good pipet and cell Scraper access. The upper triangular and wide base shape provides better stability. Flasks have volume graduations on both sides, with a special writing area as well. Plug seal caps can be used in closed systems (providing a liquid and gas-tight seal) or used in an open system (simply unscrew the cap one quarter of a turn). packaging allows flasks to remain upright, lowering the risk of contamination.