Pacific Dualies 80040 PressurePlus FM Series TPMS 4-Wheel Trailer Kit with 1-Repeater and Sensors #1/#2/#3/#4 null null null null null Adds 4-wheel trailer Includes: Model number 80002 expansion-relay and sensors #1, #2, #3, and #4 Capable of expanding up to 12-wheels Utilizes FM frequency 100 percent wireless and programmable system for maximum versatility