COOLER MASTER MasterBox Q300L Micro-ATX Mid-Tower PC Case

Product code: 245810

Product features

  • Includes case cooling
  • USB 3.0 x 2
  • Includes window
  • 4 expansion bays

Product features

  • Includes case cooling
  • USB 3.0 x 2
  • Includes window
  • 4 expansion bays
Product information
Top features: 

- Future-proof with flexibility for your system 

- Patterned dust filter keeps your build from getting clogged 

- Clean routing space for neat cable management 


Change the layout of your build and upgrade your components as often as you like with the Coolermaster MasterBox Q300L Micro-ATX Mid-Tower PC Case.

With a modular I/O panel that can be moved to six different locations within the case, you can position the case vertically or horizontally and still have easy access to all your ports.

Patterned dust filters

The MasterBox Q300L comes with 2 patterned dust filters which give your chassis a unique, stylish look while also preventing dust from getting caught inside your build and getting to your components.

With an edge-to-edge transparent side panel, you can show everyone what's inside your PC without having to take it apart - ideal for showing off your newest upgrade.

Clean routing space

When everyone can see inside your PC, you want to make sure it's looking tidy. Behind the motherboard tray is 28 mm of clear space for your cable management, so you won't have messy wires ruining the look of your build.

Technical specifications for COOLER MASTER MasterBox Q300L Micro-ATX Mid-Tower PC Case

Case format Mid Tower
Form factor Micro-ATX
Motherboard support - Micro-ATX
- Mini-ITX
Case material Steel
Window material Plastic
Case bays - 2.5" bays x 2
- 3.5" bay x 1
Expansion slots 4
External connections - USB 3.0 x 2
- 3.5 mm jack x 1
Fan mount locations - Front: (x2) 120/140 mm
- Top: (x2) 120 mm
- Rear: (x1) 120 mm
- Bottom: (x1) 120 mm
Radiator mount locations - Front: (x1) 120 mm / 240 mm
- Rear: (x1) 120 mm
Fans included 120 mm rear fan x 1
Window Yes
Maximum component size - Maximum GPU length: 360 mm
- Maximum CPU cooler height: 159 mm
- Maximum PSU length: 160 mm
Colour Black
Box contents - Cooler Master MasterBox Q300L ATX Mid-Tower PC Case
- 120 mm rear fan x 1
Dimensions 378 x 230 x 387 mm (H x W x D)
Weight 3.7 kg
Manufacturer’s guarantee 1 year
Customer reviews

Cooler Master MasterBox Q300L PC Case reviews verified by reevooReevoo

8 reviews

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(7.6 out of 10)
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Scores 7.6 out of 10 based on 8 reviews
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(10 out of 10)


London GB Geek 3D Visualization Psychologist
- Has perfect dimensions: It's is small but fits everything comfortably.

- It is light (less than 3kg)

- Includes magnetic dust filters

- It is flexible, versatile, and symmetrical. You can swap the side panels, you can use it upside down or horizontal on both sides. You can build your own dust filters to customize the aspect, you can put the power button on the bottom, front or top of either side. You can use 80, 120, or 140 fans/radiators
- "Glass" panel is actually a very light plastic, a bit too dark, and bends a little. It also catches dusts easily

- Dust filters are prone to catch dust on the sharp edges
Confirmed purchase: 03 December 2018
Published on: 31 December 2018
Price Promise, delivery & returns

You won’t get it cheaper. Our Price Promise.

Find it cheaper at any major retailer, online or instore, and we’ll match it.

If you find any of the UK’s 50 top retailers, including (but not Amazon Marketplace),, Argos, Asda, John Lewis or Tesco has the same item at a cheaper price, we’ll match it. Even if their price includes an offer-code discount, and even up to 7 days after you bought from us.

How to request a price match

Delivering your online order

Get this delivered when it suits you

We’ll show you your current delivery options for this item in checkout. Subject to the time you order, and where you want delivery, these options will include:

  • FREE standard delivery in 3-5 working days
  • Delivery next day or any following day between 8am & 5pm (£4.00)
  • Delivery in a timeslot of your choice next day or any following day (£10.00)
  • Same-day delivery in a 2-hour slot of your choice, with the last at 8pm-10pm (£10.00)
Please note: if we’re out of stock of an item but getting more in, we indicate – on listings pages and the product page – how soon we can dispatch for delivery to you. In this case, please go ahead and order, and we’ll contact you later to confirm an exact delivery date.

Availability Checker

How and when can you get hold of your selections? Finding out should be quick and easy, so with just a few clicks our Availability Checker shows you:

  • Delivery dates, time-slots and prices
  • Local stores with stock you can collect from now
  • Local stores you can get items sent to for you to collect later
To use our Availability Checker, simply:

  1. Enter a town or postcode in the box on the product page for an item you’ve selected
  2. Click on the magnifying glass
  3. Review the delivery and collection options local to you – just click on any one to add it to your basket

Stock updates

Find something you want but it’s not in stock? On the item’s product page, simply click on ‘Email me when back in stock’, and let us have your email address. We’ll let you know as soon as it’s available again.

Returns and refunds

Whether an item you’ve bought is faulty or damaged, or you’ve changed your mind, it’s easy to get a refund.

Items you haven’t opened
Within 21 days of receiving an item you paid for online, on the phone, or in store you can return it for a full refund – provided your purchase is still in its original and unopened packaging. This promise is in addition to your statutory rights.

Items you’ve opened
Within 14 days of receiving an item you paid for online or on the phone, you can return it, even if you’ve opened it. To receive a refund, you must:

  • Let us know you plan to return the item within 14 days of delivery/collection
  • Physically return it within a further 14 days.
The item must be returned in ‘as new condition’ – not used or installed, and in its original packaging. More on returns and refunds.

Order online and collect in store

Sometimes you’ll want something even quicker than we can deliver. Or you can’t be in when our van or courier would arrive. That’s why we offer you the option to order online and collect in store.
Subject to what you’re ordering and where you want to collect from, you can:

Reserve & Collect – reserve online for free and collect at a local store as soon as you like. Once reserved, your item’s held till closing time the next day, to be paid for when you collect.

Pay & Collect – pay online, and have the item sent, for free, from our warehouse to a local store for you to collect. Starting on the date the item arrives in store – which you choose in checkout – you have 28 days to collect it.

Your fastest way to order online for collection is to use our ‘Availability Checker’ feature:

  1. Enter a town or postcode in the box on the product page for an item you’ve selected
  2. Click on the magnifying glass
  3. Review the collection options local to you – just click on any one to add it to your basket

Creation - your plan Flexible credit you control

To spread the cost, pay by Your Plan, our uniquely flexible credit option. Available on all orders £99 and over, this lets you:

  • Spread the cost with monthly payments, 24.9% APR representative
  • Choose the payment term that suits you
  • No deposit to pay and choose to pay it off early at no extra cost
  • Plus once you've opened an account, you can use it to spend again in the future on anything £99 and over
Learn more

How to apply
If you’re buying this item online, you can apply for credit at checkout. Or if you’re reserving online, or shopping in store, apply here.

DSG Retail Limited acts as a credit broker and not a lender. Credit is provided by Creation Consumer Finance Ltd.
Both DSG Retail Ltd and Creation Consumer Finance Ltd are authorised and regulated by the Financial Conduct Authority.

COOLER MASTER MasterBox Q300L Micro-ATX Mid-Tower PC Case