HPI is changing some of their transmitters back to the TF-40. It seems that people would rather pay a little extra to make sure their trucks don’t randomly disconnect and fly off a cliff.
A few models such as the Sprint 2 Flux, Sprint 2 Sport, Mini Savage XS Flux, Blitz Flux, Trophy Buggy Flux, and the Bullet MT / ST Flux that initially came with the cheaper TF-11 2-Ch Transmitter are now coming again with the TF-40 3-Ch Transmitter.
Whichever one you use, make sure you have a matching receiver. They are not cross-compatible but are clearly marked “RF-11” or “RF-40”.