Here are some of the benefits of using a caddy for SSD and HDD, optical bay 2nd hard drive caddy, caddy 9.5mm for laptop:

Increased storage capacity: A caddy allows you to add a second hard drive to your laptop, which can increase your storage capacity by up to 2TB.
Faster performance: A caddy can improve the performance of your laptop by allowing you to install an SSD in the optical drive bay. SSDs are much faster than traditional hard drives, so they can make your laptop boot up faster, load applications faster, and transfer files faster.