8 smoke alarms 110 VAC w/ 9 VDC battery backup with connectors. They will interconnect if you want. These are 8 years old and should have a couple more years of life. All of them are testing OK. I had nine of these installed in my house with interconnection so if one went off they all went off. One of them went bad and this model is no longer available or compatible with new ones so I had to replace them all.