If you're putting a soft_flask into your own range, the material is the first thing to lock down, because it affects durability, weight, printing, and cost. Almost every soft_flask on the market is either TPU or food-grade silicone. Here is how they compare for a brand placing a custom order.
TPU
TPU (thermoplastic polyurethane) is the default for running soft_flasks. It stays firm enough to hold its shape when filled, tolerates being folded thousands of times without cracking, and resists UV better than most alternatives. It also takes printing cleanly, which matters when your logo has to stay sharp. At the same volume it's lighter than silicone.
The trade-off: TPU can pick up odor or staining if dark, pigmented drinks sit in it for long periods, and it's rated for roughly 0–40°C, so it isn't for hot liquids.
Silicone
Food-grade silicone is softer and can feel more premium in the hand. It's very flexible and handles a wider temperature range. The downsides for a running flask are weight (heavier at the same capacity), a higher tendency to tear under hard repeated folding, and printing that can be less crisp. It usually costs more per unit.
Which to Specify
For a flask that lives in a hydration vest and gets folded constantly, TPU is the safer choice and the one most buyers ask for by name. Silicone makes more sense for a premium lifestyle product where feel matters more than pack weight, or where the flask won't be folded as aggressively.
Whichever you pick, specify food-grade material that is free of BPA and PVC, and ask for the test reports rather than taking the claim on trust. More on that in our guide to soft_flask certifications.
Next Steps
This is one decision in a larger sourcing process — see the full guide to sourcing custom soft_flasks for the rest. Our standard running flask, the R50044, is food-grade TPU and can be customized on size, color, valve, and branding, or contact us to discuss a material spec.