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Black micro-ATX tower with acrylic side window and perforated front panel

Cooler Master

Cooler Master MCB-Q300L-KANN-S00 Micro-ATX PC Case

SKU CH-P4NY-JX6R4 MPN MCB-Q300L-KANN-S00

Compact Micro-ATX tower with magnetic dust filters, adjustable I/O panel in six positions, vertical or horizontal orientation, 28 mm cable-routing space.

  • TypeMicro ATX Tower
  • ColorBlack
  • Case MaterialSteel / Plastic
  • With Power SupplyNo
  • Power Supply MountedBottom
  • Motherboard CompatibilityMicro ATX / Mini ITX
  • Modular I/O panel moves to six locations for flexible desk layouts
  • Case stands vertical or horizontal to fit tight spaces
  • Edge-to-edge acrylic side window shows the full build
  • 28 mm routing space behind the tray keeps cables hidden
  • Perforated front, top and bottom deliver high airflow performance

Compact Micro-ATX Tower

The Cooler Master MasterBox Q300L is a Micro-ATX tower that also fits Mini-ITX boards. It has a steel and plastic body finished in black with an edge-to-edge acrylic side panel. The modular I/O panel can be placed in six positions on either side and the chassis works in vertical or horizontal orientation. Two USB 3.0 ports and two audio jacks sit on the panel. There is one internal 3.5 inch bay and two 2.5 inch bays for storage.

Magnetic Filters and Airflow

Patterned magnetic dust filters cover the bottom intake and the perforated front, top and bottom panels promote high air performance. A single 120mm fan comes pre-installed at the rear. You can add two 120mm or two 140mm fans at the front, two 120mm fans at the top and one 120mm fan at the bottom. The power supply mounts at the bottom and the case depth accepts a standard ATX unit.

Radiator Support and Cable Space

The front supports up to a 240mm radiator while the rear takes a 120mm radiator or fan and the top accepts two 120mm fans. Behind the motherboard tray there is 28mm of routing space for clean cable management. Four expansion slots are available for add-in cards. No hot-swap bays are included. The open perforated design aims to sustain thermal performance during extended workloads.

Highlights

  • Modular I/O panel moves to six locations for flexible desk layouts
  • Case stands vertical or horizontal to fit tight spaces
  • Edge-to-edge acrylic side window shows the full build
  • 28 mm routing space behind the tray keeps cables hidden
  • Perforated front, top and bottom deliver high airflow performance

Specifications

BrandCooler Master
SeriesMasterBox Q300L
Part NumberMCB-Q300L-KANN-S00
TypeMicro ATX Tower
ColorBlack
Case MaterialSteel / Plastic
With Power SupplyNo
Power Supply MountedBottom
Motherboard CompatibilityMicro ATX / Mini ITX
Side Panelwith Side Window
Dust FiltersBottom
Internal 3.5" Drive Bays1
Internal 2.5" Drive Bays2
Hot-Swap Drive Bays0
Expansion Slots4
Front Ports2 x USB 3.0, 2 x Audio
Fan OptionsFront - 2 x 120mm / 2 x 140mm fan
Rear: 1 x 120mm fan (Pre-installed)
Top: 2 x 120mm fan
Bottom: 1 x 120mm fan
Radiator OptionsFront - Up to 240mm / Rear - Up to 120mm
80mm FansNo
140mm FansNo
Side Air ductYes
Max GPU Length360 mm
Max CPU Cooler Height157 mm
Max PSU Length160 mm
Dimensions15.00" x 9.06" x 15.24"
Weight8.16 lbs.
FeaturesHigh Flexibility for System Building: 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.
Minimized Dimension with ATX PSU Support: Despite the Micro-ATX form factor and the body depth and height of only 370mm x 370mm, the MasterBox Q300L can accommodate a normal ATX PSU.
Patterned Dust Filter: Special pattern on the dust filter creates a unique outlook for the chassis.
Clean Routing Space: Behind the motherboard tray, it offers 28mm wide and spacy room for hidden cable management.
Excellent The
Shipping weight4.54 kg
Package size457 × 432 × 272 mm

Questions about this item

How do I install the modular I/O panel and which orientation mistake should I avoid?

The I/O panel mounts in six positions — front, top or bottom on either side — so choose the location before securing the motherboard; the common error is fixing it after the board is in, which blocks access to the screws.

What maintenance will the magnetic dust filters need over time?

The front, top and bottom magnetic filters lift off without tools; rinse them with water, dry fully, and snap them back — no replacement parts are required.

What thermal limit appears first when the system runs sustained loads?

With only one 120 mm rear fan pre-installed, exhaust capacity is the first bottleneck; adding front intake fans or a 240 mm radiator shifts the limit to the top dual-120 mm exhaust.

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