The SST60 is a PCB made for 60% size cases. Key switches will required to be soldered onto the SST60. The SST60 is an open source design that suits tray mount or bakeneko/unikorn (O-ring mount) style cases.
If using the a O-ring mount you will need to solder on a JST Connector.
The SST60 was designed by dededecline - github for source and firmware can be found here.