Installed the RSX in my B5M and it flies. I put an 8.0 motor in it and was having problems with the RS. I know it is only rated to 8.5, so RSX replaces it. I think the battery could also be a suspect in this one as well and I changed it. Find out tomorrow at the track. Now I have RSX in all my 10th scale vehicles. This way I can upgrade the power anytime I want.