The Transition UL35

A fastpack designed to move seamlessly between paces, without stopping, adjusting or deciding in advance.

£265.00
If any sizes are unavailable, our next restock will be on September 22, 2026
Size
Typically ships within 2 weeks

Perfect additions to The Transition

Removable Webbing Hipbelt (25mm)

Removable Webbing Hipbelt (25mm)

£15.00
The Roo (Zero Waste)

The Roo (Zero Waste)

Standard / Multicoloured (Random)

£42.50
The Roo (Zero Waste)

The Roo (Zero Waste)

Standard / Black

£42.50
The Roo (Zero Waste)

The Roo (Zero Waste)

Large / Multicoloured (Random)

£47.50
The Roo (Zero Waste)

The Roo (Zero Waste)

Large / Black

£47.50
Shiny Sticker

Shiny Sticker

£2.50
Pack Liner

Pack Liner

30L

£35.00
Pack Liner

Pack Liner

40L

£40.00
Pack Liner

Pack Liner

Prospector 40L

£40.00
Pack Liner

Pack Liner

50L

£45.00
Pack Liner

Pack Liner

60L

£50.00
The Transition

A fastpack designed to move seamlessly between paces, without stopping, adjusting or deciding in advance.

The Transition gives you the freedom to change how you move as the day unfolds. Built for a close, stable fit with the comfort and capacity of a thru-hiking pack, it’s designed for long days where the pace isn’t always the same.

Run when the trail opens up. Walk when it gets steep. Slow down for a view or set out for big miles. The Transition doesn’t ask you how you hike, it gives you the freedom to choose.

The vest-style straps provide a stable fit that minimises bounce when the pace increases, while four easily accessible front pockets, a bottom pocket and dyneema stretch side pockets keep snacks, hydration and essentials within reach without breaking stride.

Made from Ultra 100X, The Transition is ultralight, tough and built for however your day unfolds.

Not about going faster. About having the freedom to change.

Features Overview
  • Vest Style Straps
  • Soft Flask Pockets
  • Newly Designed Dyneema Stretch Side Pockets
  • Roll Top Closure
  • Roll Top Zip Pocket
  • Adjustable Sternum Strap
  • Haul Loop
  • Removable Padded Back Panel
  • Whistle Sternum Strap
  • Removable Ice Axe Loop
  • Webbing Side Compression
  • Snap Fasteners
  • Bottom Pocket
  • G-Hook Closure

Explore Full Features

View details

Find your hip measurement

Put your hands on your hips. This is normally a good cue for where you're going to wear your hipbelt and it's usually about an inch or two below your belly button. Take your tape measure and wrap it around this point. Where the tape measure overlaps is your measurement. Take a look at the chart below to see what size you are. If you are in between two sizes, going for the smaller of the two will ensure a good fit - trust us on this. 

Hipbelt Size Inches Centimetres
A 26 - 28 66 - 71
B 28 - 30 71 - 76
C 30 - 32 76 - 81
D 32 - 34 81 - 86
E 34 - 36 86 - 91
F 36 - 38 91 - 96
G
 38 - 40 96 - 101
H 40 - 42 101 - 107
I 42 or above 107 or above

 

If your measurements fall outside of the ranges in this table, please email us at hello@atompacks.co.uk. We would love to help you get the perfect fit! 

Perfect Hipbelt Fitment

Specifications

Starting weight

545 g

19.2 oz

Load capacity

9 kg

20 lb

  The Transition UL35
Weight
545.0 g
19.2 oz
Load capacity
9.0 kg
19.8 lb
Height fully unrolled
68.0 cm
26.8 in
Circumference at base
79.0 cm
31.1 in
Circumference at top
86.0 cm
33.9 in
Main body volume
30.0 L
7.9 gal
Side pockets volume
5.0 L
1.3 gal
Front pocket volume
4.0 L
1.1 gal
   
Key features

Vest Style Straps

The vest-style straps provide a stable fit that minimises bounce when the pace increases, and provide four easily accessible front pockets.

Key features

Roll Top Zip Pocket

An easily accessed zippered pocket above the shoulder straps that can fit those valuables. Easily fits your keys, phone, wallet and snacks.

Key features

Soft Flask Pockets

The top pockets on the vest style straps fit a 500ml soft flask snugly, with an adjustable elastic loop to hold it in place.

Key features

Newly Designed Dyneema Stretch Side Pockets

The same shape as our regular side pockets, but made from Dyneema Stretch fabric, these pockets are ultra-versatile. They will hold 2 x 1L bottles, or cinch them right down to nothing.

Key features

Vest Style Straps

The vest-style straps provide a stable fit that minimises bounce when the pace increases, and provide four easily accessible front pockets.

Roll Top Zip Pocket

An easily accessed zippered pocket above the shoulder straps that can fit those valuables. Easily fits your keys, phone, wallet and snacks.

Soft Flask Pockets

The top pockets on the vest style straps fit a 500ml soft flask snugly, with an adjustable elastic loop to hold it in place.

Newly Designed Dyneema Stretch Side Pockets

The same shape as our regular side pockets, but made from Dyneema Stretch fabric, these pockets are ultra-versatile. They will hold 2 x 1L bottles, or cinch them right down to nothing.

Move at your pace with the Transition.
G-Hook closure.
The Transition on the move.
The transition at camp
The Transition

Needs met.

The Transition. Any Pace. Any Day

All our bags are designed and tested to meet a specific need. Each item is built by hand to our incredibly high standards right here in our Keswick workshop.

Features

Vest Style Straps

The vest-style straps provide a stable fit that minimises bounce when the pace increases, and provide four easily accessible front pockets.

Soft Flask Pockets

The top pockets on the vest style straps fit a 500ml soft flask snugly, with an adjustable elastic loop to hold it in place.

Newly Designed Dyneema Stretch Side Pockets

The same shape as our regular side pockets, but made from Dyneema Stretch fabric, these pockets are ultra-versatile. They will hold 2 x 1L bottles, or cinch them right down to nothing.

Roll Top Closure

The closure has a 15mm buckle and can be clipped together and rolled down, dry-bag style.

Roll Top Zip Pocket

An easily accessed zippered pocket above the shoulder straps that can fit those valuables. Easily fits your keys, phone, wallet and snacks.

Adjustable Sternum Strap

Move the sternum strap elastics up or down and hook them onto any of the daisy chain loops to suit your body.

Haul Loop

This simple webbing loop is there so you can pick up and set down your pack without putting excess strain on the shoulder straps. Using this will extend the life of your backpack and keep your shoulder straps in good condition.
Removable Padded Back Panel

Uses shaped 8mm closed cell foam. Can be removed when the pack is empty for a 25g weight reduction.
Whistle Sternum Strap

Elasticated and height adjustable sternum strap with integrated whistle.

Removable Ice Axe Loop

Made with two simple elastic loops with toggle adjusters, these allow you to connect an ice axe or trekking poles to your pack.
Webbing Side Compression

Adjustable 15mm webbing that can help compress the side of the pack or help to secure the top of a roll mat or tent

Snap Fasteners

These fasteners help secure the roll top and ensure it remains closed while rolling down and compressing.
Bottom Pocket

Easy-access bottom pocket featuring a large opening on the wearer's right and trash port on the wearer's left.

Sewn using Dyneema stretch fabric.
G-Hook Closure

The G-Hook closure allows easy and quick access without having to unbuckle.

The Transition FAQ

Can I move the elastic sternum strap?

Yes, just unhook and unthread it, then loop into onto a different daisy chain loop. Use trial and error to get it in the right place for your body.

Is The Transition waterproof?

Our packs are not waterproof.

We use highly waterproof fabrics but we do not tape the seams. Therefore some water may ingress into the pack during extended periods of rain.

What is the recommended load capacity?

You should be comfortable up to about 9kg. If you are running you might want to consider taking less because the more you carry, the more bounce you will experience.

Can I run in the Transition?

Yes! Make sure to cinch it in tight to reduce the bounce. Some bouncing is inevitable.

Can I add a hipbelt to the Transition?

Yes, we recommend the webbing hipbelt if you need the extra support
Will my soft flasks fit in the strap pockets?

We have tested a number of different soft flask shapes and sizes and they all fit, up to 500ml.

Does The Transition have padding in the back panel?

Yes, there is a 3mm removable foam pad in the back panel. The outside of the back panel is made from an airy spacer mesh which is soft and wicks sweat away from your body. 
What is The Transition made from?

Ultra 100x in the main body, with dyneema stretch front and side pockets. The side pockets are the same shape as our regular side pockets, but with more stretch.

Shipping

The current lead time for this product is 2 weeks.

How much does UK shipping cost?

For mainland UK and Northern Ireland:

Small Parcel £3.95
Large Parcel £7.95 (for orders over £140)

For Isle of Man and Channel Islands, shipping is calculated at the checkout.
How long does UK shipping take?

Please note: All items purchased from Atom Packs are subject to a lead time, any shipping times quoted start when the order is complete, not from the moment the order is placed. Current lead times can change and are displayed clearly on the site.

Accessories, when completed, are shipped to the UK using Royal Mail 1st Class. This service normally takes 1-2 days.

Backpacks, when completed, are shipped to the UK using DPD next day. This service is normally delivered on the next working day.

Keep an eye out for emails and texts from DPD.
Do you ship to Isle of Man and Channel Islands?

Yes we do!