ErgotronLX Single Monitor Arm, VESA Desk Mount – for Monitors Up to 34 Inches, 7 to 25 lbs – Low Profile Clamp, White

A little pricy, but I bought an expensive monitor so I didn't want to scrimp on a cheap arm for it.This one is very well-built and easy to assemble. My only issue with it has more to do with my desk (it's an old library table) and the low-profile mounting is the only option and even with that it's already slipped off once when I was adjusting the tension. If you have a normal computer desk I'm sure it would work perfectly.