Yesterday I installed a new Safe T Alert CO detector to replace the original. The old one had reached it's useful life. I had been using a battery operated one for a couple of years and may still use it as a back up.
The old one had a smaller compartment behind the face plate that held all the electronics so I had to increase the size of the cutout in the header. It was way easier to cut the top edge out instead of the bottom. It placed the unit higher than the old one but it doesn't look too bad. The old one was white and didn't match the Espar controls you see on the left of the header.
Easy to cut the opening a little larger and connect the two wires in the back of the unit with the wires that were already there for the old detector.
Mike