Note the size specified in the description of the installation size in the PC housing. So for installation I need a 3.5 inch plug such as former floppy disk drives.
In the framework itself but that only fit 2.5-inch disks.
Who a slot for 3.5 inch hard disks may need after the installation Size 5 1/4 view (the bays for DVD drives). This is there for multiple hard drives.