I need to use the 4-6s large lipos for my F550, they come with 12awg wires which are pretty thick, so you really need a beefy connector or its a tight squeeze into the xt60 connectors, so I stick with the XT90's for the 4-6's large 5-6amp lipos. Here are some caps to suit, thanks Dennis for the original xt-60's caps.