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Cooler Master MasterBox Q300L Micro-ATX PC Case – Compact mATX Computer Case… competes with other PC Cases products on SpecPicks. Use our Compare tool to view specs side-by-side, or browse the full PC Cases category for alternatives.

Cooler Master

MasterBox Q300L Micro-ATX PC Case – Compact mATX Computer Case with Magnetic Dust Filters, Modular Adjustable I/O Panel, Perforated Airflow Design, 1 x 120mm Pre-Installed Fan, Black

Name: Cooler Master MasterBox Q300L Micro-ATX PC Case – Compact mATX Computer Case with Magnetic Dust Filters, Modular Adjustable I/O Panel, Perforated
Brand: Cooler Master
SKU: B0785GRMPG
Price: 39.99 USD
Availability: InStock

By SpecPicks Editorial · Verified 2026-08-21

$39.99

Buy on Amazon — $39.99 Compare to similar pc cases

*Price sourced from Amazon.com. Last updated 2026-08-21. Price and availability subject to change.

Bottom line: The MasterBox Q300L Micro-ATX PC Case – Compact mATX Computer Case with Magnetic Dust Filters, Modular Adjustable I/O Panel, Perforated Airflow Design, 1 x 120mm Pre-Installed Fan, Black is a niche pick — read recent reviews before buying in the pc cases category, priced around $39.99. Read recent reviews carefully before committing.

The Cooler Master MasterBox Q300L brings cube-style Micro-ATX building to a $40 price point without forcing you into cramped compromises. Inside the compact frame you can mount Micro-ATX or Mini-ITX boards alongside a full standard ATX power supply up to 160mm long, which is unusual for a case this size. Clearance is generous where it counts: CPU coolers up to 159mm tall, graphics cards up to 360mm, and support for a 240mm liquid cooler plus up to five fans total, with one 120mm fan pre-installed out of the box. The defining trick is the modular I/O panel. Cooler Master lets you reposition…

SpecPicks Verdict

SpecPicks classifies Cooler Master MasterBox Q300L Micro-ATX PC Case – Compact mATX… as a niche pick — read recent reviews before buying in the pc cases category, based on our editorial and benchmark analysis and our ranking model that weights rating × review-volume × price-fit. Cooler Master's positioning sits within the broader category mid-tier. Use the Compare tool to put it side-by-side with two or three close alternatives before clicking through to Amazon.

Common buyer scenarios for pc cases of this kind: matching it to an existing build, replacing a failing part, or upgrading from a previous-generation equivalent. Check the spec table below against your current setup — particularly socket / form-factor / power-rating fields — and confirm compatibility on the Amazon listing before purchase. Prices, stock, and Prime eligibility update directly from Amazon's catalog and may have moved since this page was last verified.

Pros & Cons

Pros

✓ Versatile Cooling: Maximize cooling performance with a 240mm liquid cooler and 5 fans.
✓ Backed by Cooler Master's warranty and support channels
✓ Ships via Amazon with Prime eligibility and the standard returns policy

Cons

✗ Confirm socket / form-factor / power-rating compatibility against your build before ordering
✗ Price, stock, and Prime eligibility update from Amazon and may have changed since this page was last verified

Key Features

Ample Interior: Explore ample interior space for Micro-ATX or Mini-ITX motherboards, ensuring easy and future expansion
Components Clearance: Accommodates CPU coolers with a max height of 159mm, GPU cards up to 360mm, and PSU up to 160mm in length.
Versatile Cooling: Maximize cooling performance with a 240mm liquid cooler and 5 fans.
Modular I/O Panel: You have the flexibility to adjust its position at the front, top, or bottom on both sides
Edge-To-Edge Panel: Show off your meticulous build through the transparent side panel with pride.
Open Thermal Design: The perforated design on all sides promotes optimal airflow and heat dissipation

Full Specifications

Brand	Cooler Master
Color	Dark Gray
Material	Alloy Steel, Plastic
Case Type	Mini-Tower
Model Name	Q300L
Model Number	MCB-Q300L-KANN-S00
Compatibility	PC
Ample Interior	Explore ample interior space for Micro-ATX or Mini-ITX motherboards, ensuring easy and future expansion
Built-In Media	1 computer case
Cooling Method	Air
Item Type Name	grocery
Number of Fans	3
Mfr Part Number	MCB-Q300L-KANN-S00
Total Usb Ports	2

Ready to buy?

Cooler Master MasterBox Q300L Micro-ATX PC Case – Compact mATX Computer Case with Magnetic Dust Filters, Modular Adjustable I/O Panel, Perforated Airflow Design, 1 x 120mm Pre-Installed Fan, Black is available on Amazon with Prime shipping and the full Amazon returns policy. SpecPicks earns a small commission on qualifying purchases — thank you for supporting independent review work.

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*Price sourced from Amazon.com. Last updated 2026-08-21. Price and availability subject to change.