Add Dual Monitors, external keyboard and mouse to your laptop with one cable
I had to update the Thunderbolt chip firmware in my ancient Lenovo T470 Thinkpad because it was disabled. But once I did that, it worked great. Plugged it in and started configuring the displays. I can use two decent size High-resolution displays (1920 x 1080) to get my work done now. The laptop charges over the Thunderbolt connection and the keyboard and mouse pass-through works perfectly. I can use the laptop just like my desktop now.
Great value. Adds all these additional capabilities with one cable. Plug the laptop in, and boom, you're working on the big bench. You can leave the laptop closed and just use the dual monitors, or you can open the laptop for an extra display. Unplug one cable, and you're mobile.
NOTE: If your laptop needs the update to Thunderbolt chip, do it right away, or I understand you run the risk of permanently disabling the Thunderbolt interface. Lenovo website has a pretty good description describing it, but I found the ThinkPad sub-reddit very helpful in getting that bit sorted. If you have trouble getting the device to work, this is the first thing to check.
Works perfectly on my P52, even with Linux, although you need to know how thunderbolt security works to use it. Not worth $400 new to me, but used on eBay is totally worth it.