These 4 mm connectors are a solder type connector that are widely used in the RC hobby. They are by far the most popular connector for motors like 25, 30, 32, 40, 46 and 60 size motors, as well as our 60A, 80A and 100A Electronic Speed Controls (ESC's)
Brushless motors have three wires to connect to the Electronic Speed Control (ESC), so there are enough connectors included for TWO Motor/ESC connections.
We suggest using a soldering jig such as the The Jigs Up Soldering Jig when soldering these connectors. Simple insert one or more of the connectors tip-down into the appropriate size holes in the jig, then heat a connector with a soldering iron and melt a little solder into it, then insert the wire into the melted solder. Move the soldering iron away from the connector and hold the wire in place until the solder solidifies. Works like a charm, and you don't need three hands!