There are 3 versions of spektrum for 3PKs .. pick what u want that suit ur needs
Information from Spektrum : -
There are three versions of module systems available for my Futaba 3PK. What are the differences?
The standard version is the least expensive and it's compatible with the optional telemetry system. If you're more into fun running, then this is the system for you. Using this system requires that the 3PK be placed into PPM mode.
The 3PK Pro compatible version features a conformably coated receiver that resists water and dirt, an upgraded reference crystal for improved RF link performance and the module and receiver cases are smoked gray and are fuel resistant. The Pro Series version features faster response time and like the standard version, the transmitter must be programmed in PPM mode to operate. The Pro Series system is compatible with the optional telemetry system.
The HRS compatible system operates with the 3PK in high speed HRS mode, giving it the fastest possible response. In fact the Spektrum HRS compatible system can only be used in HRS mode. This system is designed for serious racers that demand the quickest possible response. Telemetry is not compatible with the HRS compatible system and only two channels (steering and throttle) are operational.