Lenovo ThinkPad Serial ATA Hard Drive Bay Adapter III - Storage bay adapter - Ultrabay Slim
Lenovo ThinkPad Serial ATA Hard Drive Bay Adapter III - Storage bay adapter - Ultrabay Slim
Designed for the Thinkpad T420s (the "Slim" model), although it will also fit in the regular T420 and apparently the T510 - but bear in mind this is the slim UltraBay adapter so it will leave a thin strip open at the top of the bay on them.