Some may say it not as stable as they would like but they didn't spend the kind of money that it would take to make it very stable .  I enjoy using as it is because it is light and it has flexibility it wouldn't have if it was built stronger.  I use my knee to stabilize it from the little bit of shaking and I use it hours at a time and I'm 77 years old.  Have to have the device as I am a care giver for my wife and work from home and have to move around the house as needed.  I think it is a get produce at a very good price.  I even bought a second one and had it shipped to my Daughter.  She works from home about 40 % of the time and she used mine over the Christmas Holiday and said she just had to have one.