Lower Bay Trays mount below the MCU board and are used for a wide range of parts. Parts compatible with the lower bay are listed here. The Trays\Lower Bay git folder is organized with subfolders for each supported part. All variations based around that part are in the same folder.
There are two types of Lower Bay Trays: half and full. A full length tray covers the mount points of two half trays and must be mounted from front to back of the case.