This is the Eagle Tree Brushless RPM Sensor. Works with all versions of the Eagle Tree MicroPower, Seagull Flight Systems and Data Recorder V2 products with firmware version 4.XX FEATURES: Measures RPM via pulses from one or two wires leading from the electronic speed control to the motor Works with all known brushless motors only-will not work with brushed motors, see COMMENTS INCLUDES: Eagle Tree Brushless RPM Sensor with motor and universal receiver connector, instruction sheet REQUIRES: Installation as described in the instruction sheet SPECS: Length: 0.73" (18.5mm) Width: 0.47" (12mm) Thickness: 0.14" (3.5mm) Weight: 0.18oz (5g) Receiver Lead Length: 11.5" (292mm) Motor Lead Length: 9.5" (241mm) COMMENTS: Brushed motor RPM can be measured with the Eagle Tree Magnetic or Optical (ETRP8001) RPM sensors. jxs 02/21/07 ir/jxs