ICY DOCK Flex-FIT Trio 3.5-5.25 inch Front Bay Conversion Kit with Additional 2X 2.5 inch HDD/SSD Bay, BPSCS27273-MB343SP, Black, 2X SSD und 1x HDD

If you have a PC case from the golden era with 5.25" bays this will fit. I wish that I had bought more, but they seem to be going out of circulation. I use one in an Optiplex 3020 MT with a 3.5" HDD + 2 SATA SSDs. This device is not meant for higher capcity 3.5" HDDs, safe bet is to stick to 4TB and below (unless your HDD has 3 mount points on each side). I also don't like that the recessed area cover could slide out of position. On my Inspiron 620 MT the recessed area is less of a concern since a flap covers it. I'm using a Corsair adapter that allows 2 SATA SSDs to occupy the 3.5" space. This gives me 4 SATA SSDs. I didn't locate any screws to mount the flex fit trio inside my case, but PSU screws worked on my 620 MT (the 3020 MT has extra screws behind the front panel). In practice your case should have active cooling if you're using these.