Purchased the promolife pediatric regulator for our oxygen concentrator. That was our first mistake. Their is no way to regulate the oxygen flow with this thing. The ball bounces around so much that you cannot even get an average read on where it's at. I spoke with 2 people at promolife who said that this is an issue with that regulator and that it should be "accurate enough." I returned the item and purchased another from a different company who concurred that this should not be happening. I'm not sure why they are selling this product and where they got the 14 reviews saying it's a great prodcuct! Maybe a few employees spending a couple hours writing them? Anyway, the icing on this cake is the restocking fee of 15% and the original shipping cost on top of the cost to return the piece of garbage. Don't expect to get any satisfaction from the "management."