USB LINK connection. Plugs into Mac/PC. Only for Kestrel 5000 series. You can NOT connect your Kestrel 5000 series to your Mac/PC via bluetooth without this Kestrel LINK Dongle. Unfortunately” you can not just buy a regular LINK dongle as you might suspect” they won’t work… it MUST be the Kestrel LINK Dongle as sold here.