ASUS A21 Mid-Tower Case (Black)

Overview

The ASUS A21/BLK/ is a mid-tower PC case designed to accommodate micro-ATX and mini-ITX motherboards, providing a sturdy steel frame paired with a tempered glass side panel for a modern appearance. It supports a flexible internal layout with dedicated bays for 2.5" and 3.5" drives, allowing users to customize their storage options. Cooling is a key focus, with space for multiple 120mm or 140mm fans and radiators up to 360mm on the front and top, plus a 120mm fan or radiator at the rear, ensuring efficient airflow for high-performance builds.

This case fits graphics cards up to 380mm in length and CPU coolers up to 165mm in height, making it compatible with a wide range of components. The front panel includes two USB 3.2 Gen 1 Type-A ports and separate 3.5mm audio jacks for easy access to peripherals. Cable management is enhanced by a 33mm rear compartment, helping maintain a clean interior and better airflow. The tool-less tempered glass side panel offers quick access and showcases your build, making this case suitable for gaming rigs, workstations, or general-purpose PCs that require a compact yet expandable chassis.

Key features

• Supports micro-ATX and mini-ITX motherboards for versatile system builds
• Flexible cooling options with space for up to three 120mm or two 140mm fans on front and top panels
• Compatibility with 360mm radiators on front and top, plus 120mm radiator at rear for liquid cooling setups
• Generous GPU clearance up to 380mm and CPU cooler height up to 165mm to fit high-end components
• Front panel includes two USB 3.2 Gen 1 Type-A ports and separate audio input/output jacks for convenient connectivity
• 33mm rear cable management compartment to keep wiring organized and improve airflow
• Tool-less tempered glass side panel allows easy access and displays internal components
• Supports BTF hidden-connector motherboards, enhancing compatibility with modern hardware
• Five full-height expansion slots provide room for additional cards and upgrades

Key specs

• Motherboard support: micro-ATX, mini-ITX
• Drive bays: one dedicated 2.5" bay, two combo 2.5"/3.5" bays
• Fan support: up to three 120mm or two 140mm fans on front and top, one 120mm fan at rear
• Radiator support: 360mm front and top, 120mm rear
• GPU clearance: up to 380mm length
• CPU cooler clearance: up to 165mm height
• Power supply length: up to 210mm
• Front panel ports: two USB 3.2 Gen 1 Type-A, separate 3.5mm audio in/out jacks
• Expansion slots: five full-height
• Rear cable management space: 33mm

Connectivity and compatibility

The front panel offers easy access to two USB 3.2 Gen 1 Type-A ports, which provide fast data transfer speeds for external drives and peripherals. Separate 3.5mm audio input and output jacks allow straightforward connection of headphones, microphones, or speakers without needing adapters. The case supports BTF hidden-connector motherboards, ensuring compatibility with newer motherboard designs that use this connector style. Its internal layout and component clearances accommodate a wide range of hardware, making it a flexible choice for various PC builds.

Installation and setup

Installation is simplified by the tool-less side panel, which uses a tempered glass window to both protect and showcase your components. The spacious interior and well-planned drive bays make it easy to install storage devices and manage cables efficiently. The 33mm rear compartment provides ample room to route cables neatly, reducing clutter and improving airflow. Support for large GPUs and CPU coolers means you can install powerful components without worrying about space constraints.

Ideal uses and environments

This mid-tower case fits well in environments where space is limited but performance and expandability remain priorities. It is a strong choice for gamers building a compact yet powerful rig, professionals assembling a workstation with high-end components, or general users who want a stylish and functional PC chassis. Its cooling flexibility and component support make it suitable for systems that require efficient thermal management, including liquid cooling setups.