Simplefirst Multi-use Mesh Lumbar Support Car Seat Support Office Chair Back Rest with Elasticated Positioning Strap

There were many similar designs on Amazon and I bought this as it was one of the lowest priced. It fitted easily on chairs, but I found it rather flimsy and does not really support the back much. In fact, as you lean back on it, the support spreads out too, not providing much support as I would like it to do.