This is the Telementry System SBS-01RM RPM Sensor (Magnet type) For the Futaba 18MZ Digital Proportional Radio Control System FEATURES: This sensor provides the RPM of a motor to the Futaba 18MZ transmitter INCLUDES: Two screws Two nuts Two cylindrical magnets Four flat washers Two lockwashers Sensor unit Adapter cable Instruction manual Warranty sheet SPECS: Length: 10" (255mm) Weight: 0.16oz (4.7g) Voltage: DC 3.7-7.4V Ramge: 37 to approximately 100,000RPM 5/17/12 pjw ir/jxs