Holiday Shipping Details & Extended Holiday Returns 
Choose Your Style
The MasterBox Q300L is your straightforward option in the MasterBox Q-series from Cooler Master, a series that might be small in size but excels in functionality, modularity, and thermal performance.
System Flexibility
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.
Magnetic Dust Filters
Patterned magnetic filters create a unique look for your chassis while keeping your system's internals free from excess dust.
Small Form Factor, ATX PSU Support
Despite the Micro-ATX form factor and the body depth/height of only 370 x 370mm, the MasterBox Q300L can accommodate a normal ATX PSU.
Edge-to-Edge Acrylic Side Panel
Show off your build through the full size transparent side panel.
Thermal Performance
The open design of the perforated front, top, and bottom guarantees excellent thermal performance.
Routing Space
A space 28mm-wide behind the motherboard tray offers open space for hidden cable management.