the OMM UltraFire 5 Vest + 2 x 350ml Flexi Flask

the OMM UltraFire 5 Vest + 2 × 350ml Flexi Flask

See our entire range from the OMM here!

The OMM UltraFire 5 Vest + 2 × 350ml Flexi Flask is a lightweight, stable and functional 5-litre running vest , designed for longer training sessions, ultra races and colder conditions where you need to carry more than just the bare essentials. It builds on the TrailFire concept’s quick access front, but adds a water-resistant roll-top compartment at the back for secure storage of extra layers and gear. The vest comes complete with two 350ml Flexi Flasks .

The UltraFire vest has an ergonomic design that stabilizes across the shoulders and midsection , allowing the lungs to expand freely even at high intensity. The fit is close to the body and the vest sits like a garment rather than a backpack. The result is minimal bounce, high comfort and efficient running even when the back compartment is fully loaded.

Storage is divided for smart access: seven easy-access pockets at the front hold energy, phone, map and small items, while the 5-liter roll-top compartment at the back is water-resistant and perfect for a jacket, reinforcements or less frequently used gear . This makes the UltraFire particularly suitable for longer, colder runs , where equipment requirements vary more during the run.

When it comes to hydration, the vest offers several options. It comes with 2 × 350 ml Flexi Flasks at the front , but the pockets can also accommodate up to 500 ml soft flasks if desired. There is also space for a hydration bladder of up to 2 liters at the back , which allows you to easily adapt the vest to distance, temperature and personal preferences.

Despite the increased capacity, the UltraFire 5 weighs only about 220 grams , making it an excellent choice when you want to carry more gear without compromising the feeling of running light.

Features & Benefits

5-liter running vest with roll-top compartment – more packing space for longer runs

Water-resistant back compartment – protects extra layers and equipment

Ultralight (approx. 220 g) – low weight despite high functionality

Ergonomic and stable fit – free breathing and minimal bounce

Supplied with 2 × 350 ml Flexi Flasks – ready to go

Flexible hydration solutions – bottles in front and bladder in back

Features

7 easy-access front pockets

5 L water-resistant roll-top pocket at the back

Ergonomic stabilization over shoulders and midsection

2 × 350 ml Flexi Flasks included

Space for up to 2 × 500 ml soft flasks at the front

Compatible with hydration bladders up to 2 L

Two secure zippered pockets

Reflective details

Breathable 3D mesh in the harness

Technical specifications

Volume : 5 L

Weight : approx. 220 g (lean weight)

Hydration : 2 × 350 ml Flexi Flasks (included)

Hydration bladder : compatible up to 2 L

Material : 3D mesh, stretch mesh, nylon (210T)

Sizes : S, M, L

Suitable for

Longer runs, ultras, trail running and training in colder conditions – when you want more pack space than in the TrailFire , but still run light, free and stable .

Care instructions

Rinse the bottles after each use. The vest can be washed on a gentle cycle according to the manufacturer's instructions and should be air dried.

The OMM UltraFire 5 Vest is a body-hugging unisex running vest with a five-liter pack volume and two included 350 ml Flexi Flasks. Choose your size according to your chest circumference and try the vest on with the pack you normally intend to wear.

Size chart

The size ranges overlap slightly, so you can adjust your choice based on how close you want the vest to fit and what clothes you wear underneath.

How is the OMM UltraFire 5 Vest sized?

The UltraFire 5 Vest has a body-hugging performance fit and should sit securely over the shoulders and around the torso. The construction is unisex, meaning you should base your actual chest measurement on your measurements rather than your usual size for women's or men's clothing.

The vest should fit close enough to minimize bounce, but not so tight that it restricts the movement of your chest and diaphragm when you breathe.

Our size recommendation

• Choose the smaller size if you are in an overlapping range and want a very close fit over thin running clothing.
• Choose the larger size if you want more adjustment space or use the vest over a shell jacket and warmer layers.
• At a chest circumference of 94–95 cm, S gives a tighter fit, while M gives more room.
• At 105–106 cm, M provides a tighter fit, while L provides greater adjustment.
• If you often fill the rear five-liter compartment, you should try the vest fully packed before deciding on a size.

How do you measure?

Measure around the widest part of your chest, just below your armpits. The measuring tape should lie horizontally and close to your body without being tight.

Please measure over the sweater or jacket that you will usually wear under the running vest.

Try the vest with packing

Fill both of the included 350ml bottles and pack the rear compartment with approximately the amount of gear you plan to carry. If you are using a hydration bladder, it should also be full when adjusting the fit.

Tighten the straps gradually until the weight is stable without the vest pressing on the chest.

Check the fit

The right size means that:

• the vest doesn't bounce or slide when you run
• you can take deep breaths without feeling pressure
• the bottles sit securely at the front
• the weight in the rear compartment does not pull the vest backwards
• the shoulder section lies stable without chafing
• the vest does not cut into the neck or armpits
• you can move your arms and upper body freely