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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 2026-07-09

$39.99

Buy on Amazon — $39.99 Compare to similar pc cases

*Price sourced from Amazon.com. Last updated 2026-07-09. 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 Master Box Q300L is your straightforward option in the lineup of the brand new Master Box Series from Cooler Master. A Series that might be small in size but excels in functionality and modularity without compromising on the thermal performance. Although the size wouldn't tell, the Master Box Q300L supports a standard ATX PSU which we don't see often in the market with this size. Based on the different system setup, the I/O panel can be adjusted to six different locations, three options at each side of the case. You can decide which setup fits your system best. Due to the cube design of…

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	Black
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 2026-07-09. Price and availability subject to change.