At its heart is a 64-bit Rockchip RK3399 system-on-a-chip (SoC) which has a relatively beefy hexa-core design. There's a quad-core 1.5GHz Cortex-A53 cluster combined with a dual-core 2GHz Cortex-A72 cluster in a big.LITTLE arrangement. There will be variants of the board available with either 1GB, 2GB or 4GB of LPDDR4 RAM. Meanwhile, Mali T860MP4 GPU is capable of supporting 4K60 video over HDMI 2.0.
On the storage front, the Rock Pi 4 includes an M.2 connector with support for NVMe SSDs up to 2TB in size and eMMC up to 128GB. With respect the connectivity, the Rock Pi 4 has all bases covered with dual USB 3.0 ports, two USB 3.0 ports and even a USB-C port. There's also the aforementioned HDMI 2.0 port, 3.5mm headphone jack with microphone, and GbE. And for those that want to leverage the hardware accessories available for the Raspberry Pi, there's a 40-pin GPIO header. The single-board computer is capable of [officially] running Debian, Ubuntu and Android.
When it comes to pricing, the Rock Pi 4 Model A is quite competitive. The 1GB model will set you back just $39 compared to $35 for the Raspberry Pi 3 B+. However, that Raspberry Pi competitor only supports USB 2.0 connectivity, 1080p output, and a more meager SoC (but you do get standard 802.11ac Wi-Fi and Bluetooth 4.2). Stepping up to the 2GB and 4GB SKUs will set you back $49 and $65 respectively.
There's also a Rock Pi 4 Model B, which supports Power over Ethernet along with 802.11ac and Bluetooth 5.0. These will be priced at $49, $59, and $75 respectively for 1GB, 2GB and 4GB SKUs. Right now, there is currently no "on sale" date for the Rock Pi 4 family.