A drive bay is a standard area for adding hardware to a computer. Most drive bays are fixed to the inside of a case, but some can be removed.
HP 2.5in HDD/SSD 2-in-1 Optical Bay Bracket

HP 2.5in HDD/SSD 2-in-1 Optical Bay Bracket

HP
£90.99
HP 1XM32AA drive bay panel Black, Green, Grey

HP 1XM32AA drive bay panel Black, Green, Grey

HP
£167.99
StarTech.com Dual-Bay M.2 NVMe SSD to PCIe x8 Removable Mobile Rack; Bifurcation Required; Tool-less Installation, PCIe Backplane w/Two Hot-Swap Drive Bays

StarTech.com Dual-Bay M.2 NVMe SSD to PCIe x8 Removable Mobile Rack; Bifurcation Required; Tool-less Installation, PCIe Backplane w/Two Hot-Swap Drive Bays

StarTech.com
£139.99
StarTech.com M.2 NVMe SSD Drive Tray for use in PCIe Expansion Product Series - Drive Tray for an Additional Hot Swappable Drive

StarTech.com M.2 NVMe SSD Drive Tray for use in PCIe Expansion Product Series - Drive Tray for an Additional Hot Swappable Drive

StarTech.com
£34.99
StarTech.com 5 Pack - 2.5” SDD/HDD Mounting Bracket for 3.5 Drive Bay

StarTech.com 5 Pack - 2.5” SDD/HDD Mounting Bracket for 3.5 Drive Bay

StarTech.com
£22.99
StarTech.com 4-Bay Mobile Rack Backplane for 2.5in SATA/SAS Drives - TAA

StarTech.com 4-Bay Mobile Rack Backplane for 2.5in SATA/SAS Drives - TAA

StarTech.com
£95.99
StarTech.com 4 Bay Aluminum Trayless Hot Swap Mobile Rack Backplane for 3.5in SAS II/SATA III - 6 Gbps HDD

StarTech.com 4 Bay Aluminum Trayless Hot Swap Mobile Rack Backplane for 3.5in SAS II/SATA III - 6 Gbps HDD

StarTech.com
£99.99
StarTech.com 2 Drive 2.5in Trayless Hot Swap SATA Mobile Rack Backplane

StarTech.com 2 Drive 2.5in Trayless Hot Swap SATA Mobile Rack Backplane

StarTech.com
£53.99
StarTech.com 5.25in Trayless Hot Swap Mobile Rack for 3.5in Hard Drive, TAA-Compliant

StarTech.com 5.25in Trayless Hot Swap Mobile Rack for 3.5in Hard Drive, TAA-Compliant

StarTech.com
£22.99
StarTech.com 2.5in SATA Removable Hard Drive Bay for PC Expansion Slot, TAA-Compliant

StarTech.com 2.5in SATA Removable Hard Drive Bay for PC Expansion Slot, TAA-Compliant

StarTech.com
£31.99
StarTech.com Black Aluminum 5.25in Rugged SATA Hard Drive Mobile Rack Drawer

StarTech.com Black Aluminum 5.25in Rugged SATA Hard Drive Mobile Rack Drawer

StarTech.com
£45.99
StarTech.com Dual 2.5

StarTech.com Dual 2.5" SSD/HDD Mounting Bracket for 3.5” Drive Bay - Tool-Less Installation

StarTech.com
£12.99