Soft Flasks FAQ
Frequently asked questions on HydraPak soft flasks.
Soft flasks are better for shorter and faster runs because they are easy to refill at aid stations and let you see how much you have consumed; reservoirs are better for long, self-supported efforts where you want maximum hands-free capacity. Soft flasks also shrink as you drink, reducing slosh and packing flat into a vest pocket. Many ultrarunners combine front-pocket flasks with a reservoir in the vest.
HydraPak soft flasks come in 150ml, 250ml, 350ml, and 500ml. The 500ml is the most popular size and fits standard vest front pockets; carry two for marathons, ultras, and hot days, and use the smaller sizes for concentrated gels and nutrition. Flasks compress as they empty, so they stay comfortable the whole run. If you are unsure about what soft flask fits best in your vest, check out our Flask Fit Finder to find the perfect fit.
Yes. HydraPak soft flasks have a large enough opening to add gels, drink mix, or DIY fuel. HydraPak has nutrition-specific flasks like our line of 150ml and 250ml SoftFlasks, but nutrition can be used in any of our flasks.
Rinse with warm water after each use, and for a deeper clean use mild soap and our Flask Cleaning Kit, or a Bottle Bright tablet. The flask and cap are top-rack dishwasher safe; where a flask has a removable hand strap, take the strap off and hand-wash it separately. Let it air-dry fully to prevent residue.
HydraPak soft flasks have a low-profile, tapered, pinch-welded base designed to fit almost any vest, belt, or pack pocket, and the 500ml size fits most vest front pockets. HydraPak's Flask Fit Finder matches a specific flask to your vest if you want to confirm the perfect fit.
