The smallest size that is genuinely useful
On budget airlines only one bag flies free: the one that slides under the seat in front of you. This model is cut for that exact allowance. The point is not to carry the most, but to carry what you need without ever meeting the sizer at the gate.
Built around the sizer, not around a wish
Ryanair has allowed a free 40 x 30 x 20 cm bag since September 2025; easyJet allows 45 x 36 x 20 cm. At 40 x 20 x 25 cm this pack clears both: stood upright, its 25 cm sits inside the 30 cm height and its 20 cm inside the depth. On easyJet there is room to spare.
It opens like a case, not like a sack
The main compartment opens to 180° and lies flat. You see everything at once instead of digging from the top. On a small bag that is the difference between packing and rummaging.
The details that matter in transit
There is also a Premium version, with a reinforced base and a dressier finish.
A USB port to charge as you walk
A USB pass-through runs through the bag and connects to your own power bank, kept in an inside pocket. No more cable dangling between bag and pocket. The battery is not supplied, and it must stay in the cabin with you, never in the hold.
A separate laptop compartment
The laptop travels in its own compartment against your back, with pockets for the charger, cables and pens. It comes out on its own at security, without unpacking the rest.
A back pocket nobody can reach
Flat against your back, this pocket stays out of reach while the bag is on your shoulders. It is the obvious place for a passport, a phone or boarding passes on a crowded train.
A strap for your suitcase handle
A strap crosses the back of the bag and slides over the telescopic handle of a wheeled case. The bag stays put and your hands stay free in the terminal.
What the airlines allow
At 40 x 20 x 25 cm this pack sits inside the free personal bag allowance of the main budget airlines, and inside the cabin bag allowance of the full-service carriers.
| Airline | Stated allowance | Category | KLOSTAIN 20 L |
|---|---|---|---|
| Ryanair | 40 x 30 x 20 cm | Free personal bag | ✓ Within it |
| easyJet | 45 x 36 x 20 cm | Free personal bag | ✓ Within it |
| Jet2 | 40 x 30 x 20 cm | Free personal bag | ✓ Within it |
| Wizz Air | 40 x 30 x 20 cm | Free personal bag | ✓ Within it |
| Vueling | 40 x 30 x 20 cm | Free personal bag | ✓ Within it |
| Eurowings | 40 x 30 x 25 cm | Free personal bag | ✓ Within it |
| British Airways | 56 x 45 x 25 cm | Cabin bag | ✓ Within it |
| Lufthansa | 55 x 40 x 23 cm | Cabin bag | ✓ Within it |
Dimensions and weight as stated by the manufacturer. Baggage rules change: always check the size printed on your own booking before you fly.
Filling it without losing the shape
A soft bag only fails the sizer when you inflate it. Pack flat rather than rolled into lumps, pull the compression strap tight, and keep the front pocket for thin items. Heavy things go against your back: the bag keeps its shape and carries better.
This colour, and the others
A light grey, softer than black and less prone to marks than a pastel. It works for a business trip as easily as for a weekend.
The same pack comes in 9 colours. The others:
Full specification
Dimensions and weight as stated by the manufacturer. Baggage rules change: always check the size printed on your own booking before you fly.
| Dimensions | 40 x 20 x 25 cm |
|---|---|
| Volume | 20 litres |
| Laptop compartment | Up to 14″ |
| Stated weight | 960 g |
| Colour | light grey |
| Opening | 180°, lies flat like a case |
| Material | High-density polyester, water-resistant layer |
| Carrying | Padded back, wide adjustable straps, chest strap, reinforced handle |
| Fittings | Suitcase strap, anti-theft back pocket, external USB port, compression strap |
The three sizes in the range
Same build, three sizes. Which one is right depends mostly on the airline you fly.
| 20 L · 40x20x25 | 24 L · 40x30x20 | 30 L · 45x36x20 | |
|---|---|---|---|
| Best for | Ryanair, Jet2, weekends away | Max free size on Ryanair, Jet2 | easyJet, week-long trips |
| Trip length | 2 to 4 days | 3 to 5 days | 4 to 6 days |
| Laptop | 14″ | 15″ | 14″ |
| You are here | See the 24 L | See the 30 L |
Common questions
Before ordering, check the size, the colour, the seller and the delivery and returns terms shown on the retailer’s page.
Does it really clear the Ryanair sizer?
Yes, stood upright: its 25 cm fits inside the 30 cm height of the 40 x 30 x 20 cm allowance and its 20 cm inside the depth. On easyJet, at 45 x 36 x 20 cm, the margin is wider still. Provided you have not packed it until it bulges.
How many days does it hold?
Two to four days for most travellers, with the compression strap pulled in. Beyond that, look at the 24 L or the 30 L in the same range.
Will a laptop fit?
Yes, in its own sleeve, with pockets for the charger and cables. The screen size it takes is listed in the specification table.
Is it comfortable when full?
The back panel is padded, the straps are wide and adjustable, and a chest strap spreads the load. At this size the weight stays modest: it is the easiest of the range to carry.
Can I take it alongside a suitcase?
A rear strap slides over the telescopic handle of a wheeled case. On a budget flight it then becomes your free bag, with the case as the paid extra.
This backpack makes excellent use of the permitted cabin-bag dimensions and holds much more than it initially appears to. The separate compartments help keep clothing, toiletries and electronics organised, while the compression straps reduce bulk. It is comfortable enough to carry, although it becomes quite heavy when packed completely full. A practical choice for short trips.
Comfortable to carry, with enough pockets to keep things organised without overcomplicating it. Ideal for quick trips, school runs to the airport, or avoiding extra baggage fees.
For the price, it’s great value — well‑made, airline‑friendly and far cheaper than most high‑street options.