SINGLE MONITOR ARM DESK MOUNT: Fits one computer screen 19 21 24 27 29 30 32 inches, with a maximum support weight of 17.6 pounds, using the 75x75mm or 100x100mm VESA square bolt hole pattern found on the back of the monitors. Comes with interchangeable C-clamp (desktop up to 3" inches thick) and grommet (up to 1.5" inches thick) base mount. GAS SPRING MONITOR MOUNT: Counter-balanced for effortless adjustments. Tension is adjusted with hex key and is turned COUNTER CLOCKWISE to increase the tension. Please see instructional video for adjustment and installation instructions.