Upgrading to Nest Learning Generation 3

[Murfice]

Have a NCM 300 unit, gas heat and electric AC (Bryant). There are 2 zone dampers with 2 White Rodgers thermostats. There are 4 wires in each thermostat, no common wire and I would like to install Nest Learning Generation 3 thermostats.
After doing some surfing on the net, several replies suggested adding Venstar add a wire adapters which will provide the 5th wire to use as the common.
I have two questions: what are your thoughts about using the add a wire adapters? And do I need to purchase 2 adapters and install for each thermostats on the 300 unit?

Thanks and awaiting replies

[Paul Z.]

You need a common wire for that stat, use the "G" green wire for common you will loss only fan control from stat, which is no big deal. Most people never use it. Call 1-800-446-3110 X490