The size of the wheel is 16x7 with 43 offset. The wheels have 67.1 mm hub rings (making them "hub centric") and I am also including the aftermarket lugnuts. The rims themselves weigh less than 14 lbs each. I do not have any centercaps, but you can find them online or on ebay if you like. If you want I can probably find a picture with them on my car.
The grounding kit is supposed to help ground the electrical connections to your chassis better. This is supposed to help smoothen out the engine due to helping the ecu and helps the electronics. Some say it helps with power, but that is just not going to happen. I got it because I had some extra electronics, like gauges and radio stuff. I had the headlights sometimes dim when the a/c turned on, it actually fixed that problem but I also replace the battery at the same time I installed the grounding kit and the ground terminal was pretty corroded. It helps with engine bay aesthetics if you run the wires neatly (second).