AAVXG0118-V3 XGuard Plus C60 V3 Power Backup System 60F w/Telemetry, Alarm, Remote Off & Radio Switch ports***NOTE***: To activate the radio switch hold the OFF button while powering the unit. To deactivate repeat the process Regarding sizes, The C30 is mostly used in models where there is little space to install a C60. The larger the size the more time you have to land but all models will give you plenty for landing for any size helicopter. The unit is now also compatible with 12V systems.