Ultraflask+ Filter Cap Size:42mm An excellent choice for lightweight

An excellent choice for lightweight backpacking

and odor resistance of Merino with the comfort of an interlock knit

and buttery soft

Materials Performance mesh upper with overlays for added durability

360-degree sun protection

Ultraflask+ Filter Cap Size:42mm An excellent choice for lightweightRun 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.