Very useful and super easy to use. This programming card is a must buy if you have a Racerstar ESC because by default the "Start Mode" is set to Medium and "Brake Force" is set to 100% on the ESC which is too much and the Start Mode set at Medium creates motor cogging if you have a heavy RC car. I usually keep mine at Start Mode - Strong and Brake Force - 25%. By the way, I can confirm that this programming card works with these two ESCs for sure:
I was but worried about it at the beginning as there was blue flashing light and I couldn't do anything. after 3 power on blue light has gone and it worked.