Yup. I mix them every time I've ever built one and I've been building since the late 60's. I'm kinda like Tony, I don't over do but I stay safe as well. There are some Hitechs I won't use if given to me But by the same Tokin, the 645 is Kind of a flagship servo for them and have used many of them. Chic, I also have that jet with another kit in the box and would have no Prob using 645's all the way around on that jet. Let me know if you want a Jetmach Sport 60 kit. That would be the next step up.