Tried to save a few dollars and bought an aftermarket timer for my air exchanger when the 28 year old one failed. That timer didn't work even though the fellow at the hardware store assured me it would. Installed it, uninstalled it, returned it to the store and purchased this one from Lifebreath. It arrived on time and works perfectly. Probably spent more on gas making the two trips to the store then the extra cost for the proper timer.