PC case Cooler Master MasterBox Q300L Midi Tower Black

The Cooler Master MasterBox Q300L is a compact Midi Tower PC case designed to combine modular layout and effective airflow in a small footprint. Its cube-inspired frame includes a removable magnetic dust filter with a distinctive pattern and an adjustable I/O panel that can be positioned in six locations to match different system orientations. Despite the compact size, the case supports a standard ATX power supply and is supplied with one 120 mm rear fan, offering practical compatibility for office or home builds.

Advantages

The MasterBox Q300L provides flexible I/O placement, support for an ATX PSU in a compact chassis, and a ventilated design with a pre-installed 120 mm rear fan to improve cooling. The magnetic dust filter with a special pattern is easy to remove and clean, and the chassis accepts both 2.5" and 3.5" drives while maintaining a small external footprint.

Suitable for

• Compact home or office PC builds
• Micro ATX or Mini-ITX motherboards
• Systems requiring a standard ATX power supply in a small case
• Setups prioritizing easy maintenance and airflow

Key specifications

• Type: PC case, Midi Tower
• Supported motherboard form factors: Micro ATX, Mini-ITX
• Dimensions (W×D×H): 230 × 387 × 378 mm
• Weight: 3.7 kg
• Drive bays: 1 × 3.5", 2 × 2.5"
• Pre-installed fans: 1 × 120 mm (rear)
• Front fan support: 120 mm, 140 mm
• Power supply: supports standard ATX PSUs (bottom-mounted); PSU not included
• Front I/O: 2 × USB 3.2 Gen 1 Type-A
• Side window: Yes
• Material: Steel, Plastic
• Colour: Black

How to use

Install a Micro ATX or Mini-ITX motherboard and route cables to the rear and bottom channels to maintain airflow. Fit the ATX power supply in the bottom compartment and secure 3.5" and 2.5" drives in the provided bays. Place additional 120 mm or 140 mm fans in supported front positions if extra intake is needed. Adjust the I/O panel to one of the six available positions to suit your desk or case orientation, and attach the magnetic dust filters as required.

Recommendations

For best thermal performance, use at least one front intake fan (120 mm or 140 mm) paired with the included 120 mm rear exhaust. Regularly clean the magnetic dust filter to maintain airflow and ensure components remain dust-free.