New in box. Still in the original bubble wrap! Opened box to verify contents. 

This is an upgraded M/Flex M2.1 model, with the Dynamic Link Arm and VESA mount slider.

Dynamic Link Arm allows for better height and side to side adjustment and has built in cable management so you can tuck your monitor cables into it.

The slider allows you to slide your monitor left to right without requiring you to adjust the distance the screen is from you. Very helpful if you decide you want to add more monitors to your setup.

100mmx100mm VESA mount.