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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
- I/O panel can be adjusted in 6 different locations and the Case can be positioned: vertical or horizontal
- Edge-to-Edge Acrylic Transparent Side Panel offers a full view inside
- Body depth height: can support normal size ATX power supply
- Front Magnetic Design Dust Filter with open perforated front, top and bottom for high air performance
- Extra space behind the motherboard tray for hidden cable management
Overview
Specs
Reviews (538)
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Patterned Magnetic Dustfilters Special pattern on the dust filter creates a unique outlook for the chassis. Modular I/O Panel The I/O panel can be adjusted to six different locations. On both side of the body you can install the I/O panel at the front, top or bottom. Multiple Positioning Options The case can be put in vertical or horizontal position. Edge-to-edge Side Panel Show off your build through the full size transparent side panel. Clean Routing Space Behind the motherboard tray, 28mm of space is offered for cable management. Performance The open design of the perforated front, top and bottom guarantees excellent thermal performance Fan and Radiator Support The front supports up to two 140mm fans and up to a 240mm radiator.
The rear supports a 120mm fan or radiator and the top two 120mm fans. All to ensure you don't have to compromise on performance
The rear supports a 120mm fan or radiator and the top two 120mm fans. All to ensure you don't have to compromise on performance
Warranty & Returns
Warranty, Returns, And Additional Information
Warranty
- Limited Warranty period (parts): 2 years
- Limited Warranty period (labor): 2 years
- Read full details
Return Policies
- Return for refund within: 30 days
- Return for replacement within: 30 days
- This item is covered by Newegg.com's 30-Day Return Policy.
- Read full return policy for details.
Manufacturer Contact Info
- Manufacturer Product Page
- Manufacturer Website
- Support Phone: 1-888-624-5099
- Support Email: customersupport@coolermaster.com
- Support Website
- View other products from Cooler Master
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The Cooler Master MasterBox Q300L is a compact Micro-ATX tower case built for budget and space-conscious PC builders who want strong airflow, flexible layout options, and a clear side panel to show off a small gaming or everyday desktop build.
Recommended For
- Budget-focused builders putting together a compact micro-ATX gaming or everyday PC who want a small footprint, ATX PSU support, and room for full-length GPUs without moving up to a larger mid-tower.
- First-time or value-conscious DIY builders who care more about price, basic flexibility, and an easy-to-place case than premium materials; community feedback often frames it as a workable low-cost case when expectations stay realistic.
- Users building in a desk shelf, tight nook, or sideways desktop-style setup who specifically benefit from the movable I/O panel and the option to run the case vertically or horizontally.
- Builders who like to customize fan layout and tune airflow themselves, especially with modest-power parts; discussions around the case regularly mention that results depend heavily on fan setup rather than stock configuration.
- Shoppers who want a compact showcase case on a low budget and are fine with an acrylic side window instead of tempered glass, mainly for simple RGB or clean entry-level builds.
Real-World Use Scenarios
- Budget micro-ATX gaming build with mid-range parts: users typically choose the Q300L when they want a small, low-cost case that still fits a full-length graphics card and standard ATX power supply; the usual experience is a workable gaming build, but better results come from adding front intake fans and avoiding especially hot components.
- Compact desk or dorm-room PC setup: people use this case when they want a smaller tower that is easier to place on or under a desk, and the practical outcome is good space efficiency with fewer layout restrictions than mini-ITX, though the interior can feel tight during the build.
- First-time PC build focused on flexibility: builders use the Q300L when they want an inexpensive case with movable front I/O and simple hardware compatibility, and the likely experience is an easy-enough first build if cable routing is planned carefully before installing all fans and drives.
- Air-cooled productivity or everyday home PC: this case is commonly a better fit for office, school, browsing, and light content-creation systems where heat output is moderate; in that kind of use, owners generally report acceptable thermals and noise without needing an elaborate cooling setup.
- Showcase budget build with visible components: buyers pick the Q300L when they want a low-cost case with a windowed side panel to display RGB fans or a neat build, and the result is decent visual presentation for the price, although the acrylic panel is more prone to scratches than tempered glass.
- User-tuned airflow build: enthusiasts often choose the Q300L only if they are willing to add fans, experiment with fan placement, or make small airflow optimizations; the expected outcome is acceptable cooling after tuning, while stock or minimally configured setups are more often criticized for restricted airflow.
Spec Summary
| Attribute | Value |
|---|---|
| Best For | Compact Micro-ATX and Mini-ITX desktop builds that need flexible I/O placement and strong airflow while still accommodating full-length GPUs and a standard ATX power supply |
| Model Identifiers | Cooler Master MasterBox Q300L — part/sku MCB-Q300L-KANN-S00 (Model Name/Style: Q300L) |
| Case Type & Materials | Micro-ATX mini-tower case in black with steel and plastic construction |
| Motherboard & Expansion | Supports Micro-ATX and Mini-ITX motherboards with 4 expansion slots |
| Drive Bays & Storage | One 3.5" drive bay plus two 2.5" bays; no hot-swap bays |
| Cooling & Fans | Air cooling design with 1 x 120mm rear fan pre-installed; supports front up to 2x120mm or 2x140mm, top up to 2x120mm, bottom 1x120mm; 80mm fans not supported; side air duct provided |
| Radiator And Liquid Cooling Support | Supports front radiators up to 240mm and rear radiators up to 120mm (suitable for a single 240mm AIO in front) |
| Clearance & Component Compatibility | GPU clearance up to 360 mm, CPU cooler height up to 157 mm, PSU length up to 160 mm |
| I/O & Front Ports | Modular adjustable I/O panel configurable in six locations; front I/O provides 2 x USB 3.0 ports and 2 x audio jacks |
| Side Panel & Visibility | Edge-to-edge acrylic transparent side panel for a full internal view |
| Dust Filters & Airflow Design | Magnetic dust filter(s) and patterned dust-filter design with perforated front, top, and bottom panels for improved airflow |
| Orientation & Cable Management | Can be positioned vertically or horizontally; ~28mm routing space behind the motherboard tray for hidden cable management |
| Dimensions & Weight | 15.00 x 9.06 x 15.24 inches (depth x width x height); weight 8.16 lbs |
| Power Supply & Mounting | Bottom-mounted PSU (no PSU included); maximum PSU length 160 mm |
| Regulatory & Safety | Includes California Proposition 65 on-product warning for cancer/reproductive harm; safety attestation true |
Reference Q&A
Q: Should I buy the Cooler Master MasterBox Q300L or the Cooler Master NR400 for a micro-ATX gaming build?
A: Choose the MasterBox Q300L if you want a smaller micro-ATX case with a flexible I/O panel and the option to place the case vertically or horizontally. Choose the NR400 if your priority is stronger out-of-box airflow and a more conventional airflow layout for hotter gaming hardware. Across official specs and repeated community comparisons, the Q300L is usually the size-focused option, while the NR400 is the easier performance-first choice.
Q: Is the MasterBox Q300L a better buy than the Thermaltake Versa H18?
A: Buy the MasterBox Q300L if compact size, movable front I/O, and flexible placement matter more than maximizing front intake. Buy the Versa H18 if you want a more airflow-oriented front design, a PSU shroud, and broader front fan and radiator support. In real buying discussions, the Q300L is typically chosen for footprint and layout flexibility, while the Versa H18 is more often chosen for a traditional budget-airflow build.
Q: Should I choose the MasterBox Q300L or move up to the MasterBox Q500L?
A: Choose the MasterBox Q300L if you are building around a micro-ATX or Mini-ITX board and want the smaller case. Choose the MasterBox Q500L only if you specifically need ATX motherboard support and are willing to accept a larger footprint to get it. The two cases share the same general design language, but the Q500L is positioned as the ATX-capable version rather than a clear upgrade in airflow or build simplicity.
Q: Is the MasterBox Q300L better for a portable or space-saving PC than a larger airflow-focused case?
A: Yes, the MasterBox Q300L makes more sense when limited desk space or easier transport is part of the decision. Its compact dimensions, light weight, and ability to sit vertically or horizontally make it more practical for dorm, office, or living-room setups than many larger airflow-first cases. A larger airflow-focused case is the better fit when you plan to run hotter components and want stronger stock cooling capacity with fewer compromises.
Q: Is the Cooler Master MasterBox Q300L a good budget case for a compact micro-ATX build?
A: Yes, if your priority is a low-cost, compact micro-ATX case with decent component compatibility. The Q300L supports Micro-ATX and Mini-ITX boards, a full-size ATX power supply, GPUs up to 360 mm, and multiple fan mounts in a relatively small footprint. The trade-off is that it behaves like a budget case: you may need to spend more time on fan setup, cable routing, and build planning than with newer or more premium alternatives.
Q: Is the Q300L good for airflow and gaming parts, or should I expect to add more fans?
A: Expect to add more fans if you are using hotter gaming components. The case includes only one pre-installed 120 mm rear fan. Its perforated design and multiple fan mounts help, but repeated buyer feedback on comparable retail pages shows that real-world cooling depends heavily on fan configuration. For entry-level or moderate-power systems it can be fine, but for hotter CPUs or GPUs, a newer airflow-focused case may be the easier choice.
Q: Will the Q300L fit a full-size graphics card and a standard ATX power supply?
A: Usually yes. Based on the product specs, the Q300L supports GPUs up to 360 mm and ATX PS2 power supplies up to 160 mm long, which covers many mainstream gaming builds. The main caution is internal clearance management: long GPUs, front radiators, and large cable bundles can make a compact case harder to work in than the raw spec sheet suggests.
Q: Who is the Q300L best suited for?
A: It is best suited for budget builders who want a small micro-ATX case, flexible I/O placement, and broad compatibility without paying for premium materials. It makes sense for first-time value builds, basic gaming systems, and desk setups where compact size matters. It is less ideal for buyers who want a quieter, sturdier, or more refined build experience out of the box.
Q: Is the Q300L a better buy than a newer airflow-focused micro-ATX case?
A: Not always. The Q300L still offers strong value if price and compactness are your main goals, but newer airflow-focused micro-ATX cases typically offer easier cable management, stronger panels, and more predictable thermals with less tuning. Choose the Q300L if you want the cheapest practical compact build and are comfortable with compromises. Choose a newer airflow case if you want a smoother build process or plan to use higher-heat components.
Q: Is the Cooler Master MasterBox Q300L a good budget micro-ATX case if airflow matters?
A: It can work for a budget mATX build, but airflow is the main trade-off. Repeated Reddit discussion describes temperatures as acceptable only with added fans and careful fan placement, while others report the case still runs warm compared with better-ventilated alternatives. If low cost and compact size matter more than top-tier thermals, it is a reasonable pick; if you are building a hotter gaming system, there are safer airflow-focused options.
Q: Who is the Q300L best suited for?
A: The Q300L is best suited for buyers who want a compact, low-cost micro-ATX case with flexible layout options and support for full-length GPUs and a standard ATX power supply. It fits entry-level to mid-range builds well. It is less suitable for users who want the easiest possible thermals, premium materials, or a polished cable-management experience.
Q: Do you need to buy extra fans for the Q300L?
A: Usually yes. The case includes only one pre-installed 120 mm rear fan, and repeated user discussion says the Q300L performs better with additional front, top, or bottom fans. For a basic build, the stock setup may be usable, but for gaming hardware or warmer GPUs, extra fans are commonly treated as necessary rather than optional.
Q: What are the main trade-offs of buying the Q300L instead of spending a little more on another case?
A: The main trade-offs are weaker airflow consistency, a more basic build quality, an acrylic side panel on the listed version, and a less refined cable-management experience. In return, you get a compact chassis, flexible I/O placement, dust filtering, and broad hardware compatibility for the size. It makes sense when price and footprint matter most, but not when build quality or thermal headroom are the priority.