How to add a 2nd HDD or SSD to a Lenovo ThinkPad T410s / T420s / T430s laptop’s Ultrabay. Compare to 43n3412. This is done by replacing the optical DVD drive with a 2nd HDD caddy via the optical drive bay (also known as the Ultrabay in Thinkpads) Note that this is for the slim “s” version. There is a different caddy for the T420 and T430 (compare to the 0A65623). The T420s and T430s uses a caddy that is 9.5mm in height. The T420 and T430 use a caddy that is 12.7mm in height.
Here’s a link to the 2nd HDD caddy adapter for the T410s, T420s, and T430s