TPU Soft Flask Manufacturer Guide: Sizes, Materials, Valves and Custom Options
For running, trail running and endurance hydration products, a TPU soft flask provides a flexible alternative to a traditional rigid water bottle.
Its collapsible body can fit into compatible hydration vest pockets, reduce in volume as water is consumed and support a range of capacities and drinking configurations.
For brands and B2B buyers, however, choosing a soft flask involves more than selecting a capacity.
TPU construction, flask dimensions, finished weight, valve design, straw configuration, printing, packaging and sample testing can all affect the final product.
At Honey Dry Bag, our current soft flask range includes models from 200ml to 1L, giving buyers options for compact running hydration, standard hydration vest applications and larger-capacity outdoor use.
This guide explains the main specifications buyers should consider when sourcing or developing a custom TPU soft flask.
What Is a TPU Soft Flask?
A TPU soft flask is a flexible hydration container that uses thermoplastic polyurethane in its flexible body construction.
Unlike a conventional rigid water bottle, the body can compress and change shape as liquid is consumed.
This makes the format particularly relevant to:
- Road running
- Trail running
- Ultramarathons
- Marathon training
- Running hydration vests
- Cycling
- Hiking
- Outdoor endurance activities
The basic operating principle is relatively simple, but the finished product can vary significantly in capacity, dimensions, weight, cap, valve and other components.
If you want a more detailed explanation of the mechanism, read our guide on how a soft flask works.
For more information specifically about the material, see What Is TPU in a Water Bottle? Material, Safety, and Soft Flask Uses.
Common TPU Soft Flask Sizes
Capacity is one of the first specifications to consider when selecting a soft flask.
Our current product range covers several capacities instead of relying on one standard size.
200ml TPU Soft Flask
A 200ml TPU soft flask is useful when compact size and low empty weight are priorities.
Our R50011 and R50031 models are both listed at 200ml with a finished weight of approximately 9g.
The R50011 200ml TPU soft flask provides an example of this compact format.
A smaller flask may be considered for shorter-distance hydration, compact running equipment or situations where a runner wants to distribute smaller quantities of fluid.
250ml TPU Soft Flask
The 250ml format provides more capacity while remaining relatively compact.
Our R50023 and R50029 models are 250ml TPU soft flasks with a listed weight of approximately 30g.
This size can help fill the gap between very small race flasks and larger running-vest hydration bottles.
300ml to 400ml TPU Soft Flask
Mid-range capacities provide another option between compact flasks and standard 500ml running models.
Our current range includes:
- R50026 — 300ml / 500ml
- R50021 — 350ml
- R50017 — 350ml
- R50012 — 400ml
The R50021 350ml TPU soft flask uses a straw configuration, illustrating how capacity and drinking system can be combined differently depending on the intended application.
The R50012 400ml TPU soft flask provides another intermediate-capacity option.
500ml TPU Soft Flask
The 500ml TPU soft flask is an important format in running and trail-running hydration systems.
Our current 500ml options include R50020, R50030, R50016 and R50044, together with several models offering 500ml as one of multiple capacity options.
For example, the R50020 500ml TPU running soft flask is listed at 500ml, approximately 25 × 9 × 6cm and 40g.
However, buyers should not evaluate capacity alone.
Two 500ml soft flasks can have different dimensions, body profiles, finished weights and drinking configurations.
These differences can affect how the flask fits and performs in a particular hydration vest.
550ml, 750ml and 1L Soft Flasks
Larger capacities can be considered when more water needs to be carried or when the product is intended for outdoor applications beyond a standard running-vest configuration.
Our current range includes:
- R50028 — 550ml
- R50018 — 750ml
- R50019 — 1L
The R50019 1L TPU soft flask is an example of a larger-capacity flexible hydration product.
These options show why a TPU soft flask range does not need to stop at the standard 500ml format.
Why Is TPU Used for Soft Flasks?
TPU stands for thermoplastic polyurethane.
It can be used to create the flexible body required for a soft hydration container.
For a finished soft flask, however, the material name is only part of the specification.
B2B buyers may also need to consider:
- Material specification
- Flask construction
- Body flexibility
- Hot-pressed or welded areas
- Neck construction
- Cap components
- Drinking valve
- Product dimensions
- Finished weight
- Intended application
Some soft flask assemblies combine TPU with other materials.
For example, our R50021 specification lists a TPU body, silicone nozzle and PP cap.
This is why buyers should evaluate the complete product rather than treating every product described as a "TPU soft flask" as identical.
If material selection is one of your main sourcing questions, our existing article on TPU water bottle material and soft flask uses provides additional background.
Bite Valve, Cap and Straw Options
The drinking system can significantly change how a running soft flask is used.
Bite Valve
A bite-valve configuration can allow a runner to drink directly from a flask positioned in a compatible hydration vest pocket.
For running applications, buyers should consider the height and position of the valve in relation to the vest pocket.
Straw
A soft flask with straw extends the drinking point upward.
This may be useful when the flask sits deeper inside a running vest pocket or when the product configuration requires easier access to the drinking point.
Our R50021 350ml soft flask is one example of a TPU soft flask with a straw configuration.
Cap and Opening
The cap system affects filling, cleaning and the overall flask configuration.
When developing a custom product, buyers should confirm the required cap and valve arrangement during the sample stage rather than evaluating only the appearance of the flexible flask body.
Soft Flask Dimensions Matter for Running Vests
Capacity alone does not determine whether a soft flask will fit a running vest.
This is particularly important for brands developing a flask for a specific vest or hydration system.
For example, different 500ml models in our range have different listed dimensions.
R50020 is listed at approximately 25 × 9 × 6cm, while R50030 is listed at approximately 27 × 6.5cm.
Both provide a nominal 500ml capacity, but their physical profiles are different.
For this reason, B2B buyers developing a soft flask and running vest together should evaluate:
- Vest pocket width
- Pocket depth
- Filled flask dimensions
- Flask body profile
- Valve position
- Accessibility while running
- Retention when the flask becomes partially empty
A physical sample can be useful when compatibility with an existing running vest is important.
We discuss this issue in more detail in Soft Flask vs Water Bottle: Which Is Better for Running?.
Custom TPU Soft Flask Options for Brands
A custom TPU soft flask project can involve more than placing a logo on an existing bottle.
Depending on the selected model and project requirements, customization discussions can include:
- Capacity
- Flask dimensions
- Body shape
- Product color
- Logo printing
- Valve configuration
- Straw configuration
- Cap components
- Packaging
- Branding requirements
For many projects, starting with an existing soft flask model can be the more practical approach.
A buyer can first identify an appropriate capacity and basic structure, then discuss branding and other required changes.
More extensive structural modifications should be evaluated separately because they can affect sampling, tooling, production requirements and cost.
OEM Soft Flask Development
For an OEM soft flask project, it is useful to begin with the intended application.
For example, tell the manufacturer whether the product is intended for:
- Running
- Trail running
- A particular hydration vest
- Racing
- Cycling
- Hiking
- General outdoor hydration
Then define the major product requirements.
These may include:
Capacity
Do you need 200ml, 250ml, 350ml, 500ml or a larger capacity?
Dimensions
Does the flask need to fit an existing vest or pocket?
Drinking system
Do you require a bite valve, straw or another configuration?
Branding
Do you need custom color, logo printing or packaging?
Estimated quantity
What is the expected order quantity?
Providing this information gives the manufacturer a clearer starting point for evaluating the project.
Sample Testing Before Bulk Production
For OEM and ODM soft flask projects, physical sampling is an important stage before bulk production.
A sample allows the buyer and supplier to confirm the agreed product rather than relying only on photographs or specification sheets.
Depending on the project, sample inspection can include:
- Product weight
- Product dimensions
- Printing
- Material and construction
- Hot-pressed areas
- Water leakage
We have published several examples from actual soft flask sample inspections after removing customer-identifying information and branding.
For example, see our 500ml Soft Flask Sample Inspection: Weight, Size, Printing and Leak Test.
Another example is Custom Soft Flask Sample Testing Before Bulk Production: A Real OEM Case.
For products using an additional carrying component, see Soft Flask With Hand Strap: A Real Custom Sample Inspection.
These reports document individual inspected samples. They should not be interpreted as a guarantee that every product or production batch has identical specifications or results.
Their purpose is to show examples of the physical checks that can be performed during real sample development.
What Should B2B Buyers Confirm Before Ordering?
Before placing a bulk order for TPU soft flasks, buyers should confirm the specifications that actually affect the finished product.
Capacity
Is the product intended to be 200ml, 250ml, 350ml, 500ml or another capacity?
Dimensions
Does the filled flask fit the intended vest pocket or carrying system?
Materials
What materials are used for the flask body, nozzle, valve and cap?
Drinking System
Does the project require a standard bite valve, straw or another configuration?
Weight
Is finished product weight important for the intended running or endurance application?
Branding
What logo, print color, print position and product color are required?
Sample Approval
Which specifications and functions should be checked before bulk production?
MOQ
Does the required order quantity match the selected product and customization requirements?
Confirming these points early can reduce unnecessary revisions during the sampling process.
Choosing a TPU Soft Flask Manufacturer
When evaluating a TPU soft flask manufacturer, buyers should look beyond a single product photograph or quoted unit price.
A supplier should be able to provide clear product specifications and discuss how an existing model relates to the buyer's intended application.
It is also useful to evaluate whether the supplier offers multiple capacities and configurations.
A broader product range allows buyers to compare different solutions before committing to a particular design.
For example, a running brand may initially consider a 500ml soft flask but later determine that a 350ml flask with a straw is more suitable for a particular vest.
Having multiple existing configurations makes that comparison easier.
Physical samples and documented specifications can then be used to confirm the selected direction.
Our Current TPU Soft Flask Range
Honey Dry Bag currently offers TPU soft flask models covering capacities from 200ml to 1L.
Our current range includes:
- R50011 — 200ml
- R50031 — 200ml
- R50023 — 250ml
- R50029 — 250ml
- R50026 — 300ml / 500ml
- R50021 — 350ml with straw
- R50017 — 350ml
- R50012 — 400ml
- R50020 — 500ml
- R50030 — 500ml
- R50016 — 500ml
- R50044 — 500ml
- R50022 — 250ml / 500ml
- R50027 — 250ml / 500ml
- R50028 — 550ml
- R50018 — 750ml
- R50019 — 1L
Rather than selecting a model only by capacity, buyers can compare dimensions, finished weight and drinking configuration according to the intended application.
For a standard running-oriented option, review the R50020 500ml TPU soft flask.
For a smaller flask with a straw configuration, review the R50021 350ml TPU soft flask.
For a larger-capacity option, review the R50019 1L TPU soft flask.
TPU Soft Flask vs TPU Water Bottle
The terms TPU soft flask and TPU water bottle can overlap, but they do not always describe exactly the same product format.
"TPU water bottle" is a broader search term that may refer to different flexible hydration containers using TPU.
A running soft flask is more specific.
It commonly combines:
- Flexible TPU body construction
- Compact body profile
- Sports-oriented capacity
- Bite valve or drinking nozzle
- Compatibility with running or hydration equipment
Similarly, the term collapsible water bottle describes a broader category of bottles that can reduce in size when empty.
A running soft flask can be considered a specialized flexible or collapsible hydration format, but not every collapsible water bottle is necessarily designed as a running soft flask.
For a detailed material explanation, read our TPU water bottle guide.
Final Thoughts
There is no single TPU soft flask specification that is appropriate for every running or outdoor hydration product.
A compact 200ml flask serves a different purpose from a standard 500ml running soft flask, while a 750ml or 1L model addresses another set of hydration requirements.
For B2B buyers, a practical approach is to define the intended application first and then compare:
- Capacity
- Dimensions
- TPU construction
- Valve configuration
- Finished weight
- Running vest compatibility
- Customization requirements
When custom branding or product modifications are required, physical sampling and specification confirmation should take place before bulk production.
Honey Dry Bag focuses on TPU soft flask products for running, trail running, endurance sports and related outdoor hydration applications.
If you are developing a custom soft flask, contact us with your intended application, target capacity, estimated quantity and customization requirements.
We can then discuss an existing model or customization direction appropriate for the project.
