We bought this because it's the same model that was put in the house when it was built. The original started beeping and after we figured out we weren't going to die from Carbon Monoxide poisoning, we ordered this to just plug and play into the portion of the original that we didn't want to remove from the ceiling. So, I'm giving this 4 stars as it was great for interchangeable part usage and we are still breathing just fine =)
Rating: [4 of 5 Stars!]