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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.

  • Max graphics card length360 mm
  • Housing materialSteel / Plastic
  • Power supply mountingBottom
  • Supported motherboard sizesMicro ATX / Mini ITX
  • Side panel typeWith Side Window
  • Dust filteringBottom
  • 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.

How it compares

Measured against everything we stock in Tower & Desktop PC Cases, at today’s prices. Recalculated every night.

Price $32.99
Cheaper than about 94% of the 1,468 comparable items (median $100.99).
Max graphics card length 360 mm
Lower than about 70% of the 894 comparable items (median 400 mm).

New to this? Buying PC parts with Monero — what to check, what it costs to pay, and what is never asked for.

Specifications

Product
Brand nameCooler Master
Product lineMasterBox Q300L
Part numberMCB-Q300L-KANN-S00
Product typeMicro ATX Tower
Product colorBlack
Storage
3.5-inch internal bays1
2.5-inch internal bays2
Hot-swappable bays0
Ports & slots
Expansion card slots4
Front panel ports2 x USB 3.0, 2 x Audio
Power
Power supply includedNo
Size & build
Max graphics card length360 mm
Housing materialSteel / Plastic
Power supply mountingBottom
Side panel typeWith Side Window
Dust filteringBottom
Fan mounting optionsFront - 2 × 120 mm / 2 × 140 mm fan
Rear: 1 × 120 mm fan (Pre-installed)
Top: 2 × 120 mm fan
Bottom: 1 × 120 mm fan
80mm fan countNo
Product dimensions15 in × 9.06 in × 15.24 in
Product weight8.16 lb (3.7 kg)
Shipping weight4.54 kg
Package size457 × 432 × 272 mm
Compatibility
Supported motherboard sizesMicro ATX / Mini ITX
Radiator supportFront - Up to 240 mm / Rear - Up to 120 mm
CPU cooler height limit157 mm
PSU length limit160 mm
More details
140mm fansNo
Side air ductYes

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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