This is designed and made by me at my home. 3D printed for you in Texas.

This is 2oz of PLA (Polylactic Acid) plastic that was 3d printed. Designed by me to help my father turn on and off his oxygen bottles himself. He was having a hard time with the wrench finding the hole and when he did the wrench would hit the cart or the regulator and would not let him turn the valve or worst, he would think that he had closed the tank when he had not. This knob is not large enough to interfere with the cart and it sets above the regulator, being round you do not have to remove it to turn the valve completely open or closed. The Knob loosely slides down the valve post. and is easy to lift off so you can remove the regulator to swap out the tank. Then drops back in place after the regulator is placed on the new tank. The Knob is 3.25" around with (5) 3/4" recesses to make the grip and is just over 3/4" thick so it is easy on the hands all the edges are rounded over. There is a label molded deep in the top "Oxygen Knob" so if it is gets misplaced, you'll know what it is for.

I have a second product coming out. It is a tool to remove the pesty oxygen hose from the regulator. The Oxygen Hose Removal Tool is also PLA plastic 7" long designed for older hands with soft edges and a large hole to hang on the cart hook. Simply slide the tool between the hose and the regulator and press down if the hose does not come off, slide in a little more and press down. The stepped contact point will give you the leverage you need to get the hose off easy and quick.