I ordered both this foot rest and the Humanscale FM 300 to test out. Both are well made, however this model (F500K) gently presses you back in your seat for good posture. An ergonomic expert, who happened to recommend this footrest, told me that ironically the best ergo chair is often times a standard one with armrests and good lumbar as we should be sitting back vs forward...a lot of backless ergo chairs foster or can't prevent cheating with bad posture. This footrest naturally puts you back in your seat and has an absolutely smooth and quiet rocking motion. The FM 300 was well constructed, however you hear the rocking noise back and forth. It's not cheap, but well worth it!