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
*Price sourced from Amazon.com. Last updated 2026-07-06. 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.
*Price sourced from Amazon.com. Last updated 2026-07-06. Price and availability subject to change.
Related PC Cases
More guides & deep dives from the SpecPicks archive
Browse all articles & guides →- Best 1440p Gaming GPUs in 2026
- Best Budget Gaming PC Build 2026 — ~$1,000 ($800 on Sale)
- Emulation Hardware in 2026: FPGA, Software, and Cart-Reader Ecosystems
- RTX 4070 Super vs RX 7800 XT — Which to Buy in 2026
- How to Build a Windows 98 Retro PC in 2026
- Best Retro Handhelds in 2026 — From $35 to $500
- The Complete Voodoo5 5500 AGP Driver Guide (2026 Edition)
More reviews from the SpecPicks archive
Browse all reviews →- Steam Controller (2026) Scores 83/100 in Early Reviews
- How to Run a Public Website on a $10 ESP32 Without Servers
- ComfyUI on an RTX 3060 12GB: Stable Diffusion Throughput and VRAM Limits in 2026
- SANSUI 27" 4K vs KOORUI 27" QD-Mini LED for PS5 & 4K Gaming in 2026
- Build a RetroPie Arcade on a Raspberry Pi 4 8GB in 2026
- Sound Blaster Audigy FX Install Guide for Win98 SE Period-Correct Builds
- Logitech Gaming Mouse Deals Hit 47% Off for Prime Day 2026
- Kimi-Dev-72B Local Coding Benchmarks: VRAM Required, Tok/s, and How It Stacks Against DeepSeek V4 and…
- GeForce 4 Ti 4600 Won't Boot Past POST: AGP Voltage and BIOS Field Guide
- Best Gaming Controller for PC and Console in 2026: 5 Picks Compared
- GLM-5.2 on 12GB VRAM: Quantization and Speed on the RTX 3060
- Kimi K2.7 Code on an RTX 3060 12GB: Can a $300 GPU Run It?
- Best Budget Gaming Mouse + Mousepad Combo Under $80 in 2026
- pxpipe Hides Prompts in PNGs to Cut Claude Code Tokens 70% — Or Just Run Local on an RTX 3060
- Running a Modern SATA SSD in a Windows XP Retro Gaming PC
- GPT-5.6 Sol Now Requires US Government Approval Per Customer
- Best Internal SSD for a PS4 Pro Upgrade: 2.5" SATA Picks That Cut Load Times
- How to run DeepSeek-R1 32B on NVIDIA GeForce RTX 5080
- Self-Host Jellyfin on a Raspberry Pi 4 8GB: Measured Power and Perf
- Gemma-4-Harmonia-31B Uncensored on RTX 3060 12GB: Quantization, VRAM, and tok/s
- Best 4K Monitor for PS5 (4K/120Hz) in 2026
- Best GPU for 1080p Esports in 2026: Why the RTX 3060 12GB Still Delivers
- Build a Pi Zero W Retro Handheld in 2026: Full Parts List and Setup
- Jetson Orin Nano Super vs Raspberry Pi 5: Real Edge-AI Benchmarks (2026)