Hermell Products LC2235GY Memory Foam Trisectional Lumbar Cushion

I like it a lot and it is a great buy, but because it is so thick you need a slightly deeper chair because it forces you to the very front of your chair. It was fantastic on my slightly deeper chair at home and forces me to use correct posture. It also happens to make a great foot rest if you get tired of sitting correctly and just want to slouch.