This is the Manfrotto (1052BAC) Black Alu Compact Stand Pack of 3.

Each stand rises to a maximum height of 7.75' (2.3 m), and is air cushioned. Formerly known as a "Stacker", these stands now have what is called the QSS - Quick Stand System.

When folded, these 3 stands may connected to each other to ease storage or transport. Air cushioning protects fingers and mounted equipment.

If the stand sections are not sufficiently tightened, mounted equipment eases down to minimum height instead of slamming down suddenly.