Danny wrote this on his facebook page on them.

"Just added the SMC Ex-Cap to the website. The Ex-Cap is capacitor that can go on any ESC and give a bit more power. This is especially helpful in stock Blinky. We expect the first shipment of Ex-Cap to arrive with our ESC shipment. Not sure of the exact date yet but it should be end of next week or the following week."

"Capacitors on ESCs are legal so this capacitor is legal unless ROAR , TOUR or whoever makes the rules decide that capacitors aren't legal."

"Yes it gives a bit more power. Don't buy this thinking it will give you a lap but if speed is important to you then this will give you a bit more."

"Yes it will fit on a GTB or any other ESC. They go where your current capacitor is soldered which is on the positive and negative leads. Not sure on how it effect temps but I doubt it makes a big difference in temp. Once again this will give a small improvement in power and is for those who want to have everything on their side when it comes to performance. I don't want guys to buy these and expect them to see a big improvement as this will not be the case."