Works as intended, & as not intended. Lemme' 'splain.
My wife needed some extra support from her inexpensive home office chair since she's been working at home due to the COVID!!!!! (sorry, ran behind my couch for a moment).  I bought these for her & she's used it every day for almost two months & says it's been a back saver. As I've worked at home for years, I've got a really nice chair & didn't need the second unit. I ended up using it for a somewhat unorthodox application,  on my Amazon Purchased Innova ITX9600 Inversion table (a great investment by the way).  It gives a bit of support while tipping back, then aids in letting the table stay perfectly vertical as I hang. For some reason, my table wouldn't stay completely vertical unless I held it in that position using the side rails. This solved my problem.
Rating: 5 stars