Review on Flex-FIT Quattro MB344SP: Tool-Less Dual 2X 2.5” HDD/SSD Mounting Bracket (4 Bays) for External 5.25” Bay by ICY DOCK by Jeff Wieczorek

Plastic. This is fine as long as you don't plan to subject your computer to 9G shocks and/or a jackhammer. It actually comes with a big gap door on the front, you have to push it off on the back. It is in fact a slab that acts like a guillotine being placed on it. Once the adapter is installed in the bay, the door cannot be removed until you remove the adapter from the computer. The door will also be about 1/4 inch or about 1 cm from flush, so there will be a gap and it will look like a 1990's tape deck. I use it with two 2.5" drives and one 3.5" drive. , you CANNOT use 90 degree connectors as the bottom HD will be in the way, so direct connections only. It's plastic, so you can modify it to fit your case with relative ease without exposing the front. 2.5" bays have a quick release latch. The problem is that the tabs CANNOT move while the adapter is in the case. If you need to remove a 2.5" hard drive, you must remove the entire adapter. Not terrible, but not great either. Works. Cost me $8.