RX-381 2.4GHz FHSS-3 3 Channel Receiver, and is intended for use with the M11X, EXZES X, MT-4, MX-3X, and any other Airtronics FHSS-3 compatible surface transmitter. This digital high response Airtronics receiver is slightly lighter than the receiver included with the M11X, and over 1.5g lighter than the receiver found with the MT-4 radio system.