Review on TPU Folding Flask: TRIWONDER Soft Flasks Collapsible Water Bottles For Hydration Pack - Ideal For Running, Hiking, Cycling & Climbing by Reid Rickerson

Perfect soft flasks to fit in the Aonijie 18L hydration running pack or to use solo and carry. Each flask holds 500 mL beverage which is ideal for about 2.5-5 miles of running depending on intensity. I've used these with hydration electrolyte carbohydrate solution and also just water, and they work easily and efficiently. The bottle does not take much bite force to open the bite valve and get a squirt of liquid, liquid is also ejected with very little squeeze pressure. Wouldn't use any other soft flask for running or exercise! I'll keep coming to Aonijie for my hydration and exercise/trail running needs!