RasPiKey is a 16GB or 32GB (select version above) eMMC module which can be inserted into your Raspberry Pi’s Micro SD card slot.
It works like a micro SD card but with better read/write performance (especially on 4k read/write) and has a longer lifetime (increasing the chance of surviving a power loss).
The RasPiKey has Raspberry Pi OS preinstalled and allows you to configure SSH login and your Wi-Fi connection before booting your Raspberry Pi. As a result, you can use your Raspberry Pi without a display, keyboard and mouse, and access your Raspberry Pi via an SSH session.
The RasPiKey is a “plug and play” accessory for most Raspberry Pi models. If you have Raspberry Pi 4B from a rather old batch which has rather old firmware that cannot recognise the RasPiKey, you may need to update the bootloader of your Raspberry Pi 4B beforehand (please find more details in the user manual).
RasPiKey supports all Raspberry Pi models.
Raspberry Pi 3B+ Benchmarks
RasPiKey has much better read/write performance than all SD cards on a Raspberry Pi 3 and 3B+. Below are the benchmarks (using the same method here) on Raspberry Pi 3B+:
Raspberry Pi 4 Benchmarks
By upgrading the firmware on Raspberry Pi 4B, DDR52 mode will be supported and RasPiKey will offer much better performance (please find details in the user manual). Below are new benchmarks for RasPiKey on Raspberry Pi 4B (with DDR52 mode supported):
You can find the user manual here: https://www.uugear.com/doc/RasPiKey_UserManual.pdf