I haven't used/tried them before but it certainly looks simple enough to make myself. Based upon the photo, it's just a 10v, 1700 microfarad capacitor rated for 105 degrees Centigrade soldered and heat-shrunk to leads termined with a universal servo connector?
I use them, and so are others. It keeps the voltage at 5 volts when you turn on a high current device, like the pump motor. If the voltage drops for just 10ths of a second the receiver can come unlocked, and then you lose control. They came out with those when the flyers all started loosing their planes, not long after the radio came out. Mark had the issue in his Yamato, when he turned 2 pumps on at the same time. With the cap, he had no issues.
