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Cooler Master MasterBox Q300L

A compact micro-ATX enclosure whose smaller board support should be decided first.

Check with my buildRead the specifications ↓
The decision

The original MasterBox Q300L is a compact route for a micro-ATX or Mini-ITX build. Its nominal long-GPU clearance does not turn it into an ATX motherboard case, nor eliminate the need to plan airflow. Check the complete cooling and cable layout before choosing it merely because individual components appear short enough.

Consider it when

  • A smaller motherboard and a deliberately compact component list.
  • A build whose ATX PSU can fit the 160 mm PSU space with cable routing considered.

Look again when

  • A full-size ATX motherboard.
  • A tall dual-tower cooler or front radiator paired with a long graphics card without a joint fit check.

The checks that can change your choice

159 mm is the cooler ceiling

Check the installed fan height, not only the bare heatsink. A cooler listed at exactly the limit deserves measurement and a revision check; a larger case offers more room for uncertain dimensions.

Distinguish the original Q300L

The catalog refers to MCB-Q300L-KANN-S00. Follow that model’s manual for front 120/240 mm and rear 120 mm radiators; do not borrow mounting options or connector details from later Q300L variants.

Published specifications

Mini-tower case; micro-ATX/Mini-ITX; GPU length up to 360 mm; CPU cooler height up to 159 mm.

BrandCooler Master
Exact modelMasterBox Q300L
Form factorMini-tower
Case motherboard supportmicro-ATX, Mini-ITX
Case GPU length limit360 mm; cooling and layout can reduce this
Case CPU cooler height limit159 mm
Case PSU formatsATX
Case PSU length limit160 mm; allow cable and drive-cage space
Radiator mount: front / 120 mmCheck mounting dimensions and occupied positions
Radiator mount: front / 240 mmCheck mounting dimensions and occupied positions
Radiator mount: rear / 120 mmCheck mounting dimensions and occupied positions

Original MasterBox Q300L, MCB-Q300L-KANN-S00. Manufacturer specifies bottom-mounted ATX PS2 power supply and 160 mm PSU clearance.

Catalog record checked . Manufacturer specifications. The individual references below show the dates used for these model notes.

A different choice worth checking

LIAN LI LANCOOL 207 Black (LAN207RX)LANCOOL 207 fits an ATX build into a more compact arrangement by making specific choices about board width and PSU placement. Its four included fans are a useful starting point. Decide on the power supply, cable routing and drive count early; those details matter more here than simply checking that the board says ATX.Read this model’s tradeoffs ↗Fractal Design Meshify 2 Compact Black TG (FD-C-MES2C-03)The Meshify 2 Compact is worth considering when a full-size tower would waste room. Its 341 mm graphics-card allowance assumes a front fan, and a front radiator changes that space. The PSU decision also depends on whether you retain the drive cage, so settle the storage layout before buying the power supply.Read this model’s tradeoffs ↗

These alternatives address related choices. Recheck their platform, connections and fit before treating one as a replacement.

Parts lists using this exact model

These lists show the surrounding components and the tradeoffs. They are editable planning examples, not measured systems.

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Sources and review notes

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