Run fast, filter faster. The UltraFlask+ Filter Cap threads seamless onto all of HydraPak's 42mm running flasks and handhelds for a lightweight, straightforward filtration solution. Featuring a traditional bite valve and cap design, runners can drink freshly filtered water directly through the high-flow Blaster valve.*Effectively removes common waterborne bacteria, such as E.coli (99.999%) and parasitic cysts (99.9999%) per HSF 42.