I'm running one in my 2011 300 EStart. It works great, I 'll look for the part number number when I get home. It spins the starter a lot faster and I haven't had any problems. Just don't leave your key on. I heard from the reps that if you totally discharge it, the battery is toast. I've had mine for about 18 months, I haven't had any problems and I've never had to use a tender/charger. Its also very light.