I would like to install a 2.5" HDD in the 3.5" caddy/slot.  I already have 2.5" drives occupying the two remaining slots.

The reason for going with 2.5" is for lower noise, power consumption and heat.  I also had a poor experience with a faulty 3.5" drive purchase.

What do I require in terms of a caddy?  At the moment there is a blue plastic caddy for the 3.5" drive.  Does that get entirely replaced or is there an adapter that fits within the existing plastic caddy?