One is Open Box, it contains only the Nest Power Connector - See Pictures!Nest thermostats are designed to work without a C wire in most homes. But some systems may require a C wire for consistent power to your Nest thermostat. The Nest Power Connector is an affordable C-wire substitute for homes that don't have one. It doesn't require any new thermostat wiring. And with simple instructions, you can even install it yourself.HighlightsC-wire substitute for Nest thermostats: nest thermostats are designed to work without a C wire in most homes, but for some systems, including heating-only, cooling-only, zone-controlled, and heat pump systems, you'll need a nest power connector or C wireWorks with 24 VAC systems: nest power connector is only compatible with 24 VAC systems, so it won't work with millivolt or high voltage systemsInstallation is simple: attaches to your furnace, air handler, or zone controller, and comes with simple instructionsCosts less than a new C wire: nest power connector is an affordable C-wire substitute that's designed to be compatible with nest thermostats - and costs much less than hiring an electrician to install a new C wire through your wallsThoughtfully designed: nest power connector resists dust and water, and is made from 46% recycled plastic, wire connectors and sticky pad are designed for easy, mess-free installation