It is meant to be combined with the FCHUB-A5 on frames where you cannot soft mount the FC - It incorporates 30x30 board mount as part of its upper deck structure.
Example of frames would be the ARC200, Emax X5, ImpulseRC Helix. or picture below

If you are looking for a 20x20mm option check out the Matek F411-MINI instead.

• MCU: 168MHz STM32F405
• IMU: 32K ICM20602 accelerometer/gyro (SPI)
• Support 32K Gyro update & 16K PID Loop
• OSD: BetaFlight OSD w/ AT7456E chip
• Blackbox: 32M(256) Flash
• VCP, UART1, UART2, UART3, UART4, UART5
• Built in inverter for SBUS input (UART2-RX)
• PPM/UART Shared: UART2-RX
• SoftSerial & Camera control supported on S5 & S6
• Battery Voltage Sensor: 1:10
• Current Sensor: No (FCHUB-A5 option)
• BEC 5V: No (FCHUB-A5 option)
• LDO 3.3V: Max.300mA for Spektrum RX
• I2C1 SDA & SCL available
• WS2812 Led Strip : Yes
• Beeper : Yes
• RSSI: Yes
• 2x LEDs for FC STATUS (Blue, Red)
• 6x PWM / DShot outputs without conflict
• 5x UARTs
• 1x 14pin top mounted FFC Slot for FCHUB-A5 connection
• 28x28mm PCB with 20mm mounting holes
• w/ 6x silicon grommets M4 to M3
• w/ 6x brass grommets M3 to M2
• w/ 2x 0.5mm*14Pin 3cm Flexible Flat Cable
• MatekF405 Target
• Firmware based on OpenSource BetaFlight