Does your new trailer have turn signals independent of the brake lights? (like you bike) If so, you will need a five pin connector of some type (round, flat, square) If your trailer turn signals share the same lights as the brakes, it is set up for a four pin connector. If this is the case, you have to make a choice, either add independent turn signal lights to the trailer or get a five to four converter for your bike. It will work either way and one way is not necessarily harder or more expensive than the other, just a choice.