4-5mm Universal Male Gold Plated Spring Connector - Low Profile (10pcs)

Pro Tip: If you find the bullets hard to plug in to your battery, take a set of needle nose pliers and gently squeeze two of the four prongs, turn the plug and repeat on the other two prongs. If the plug is too loose take a small Phillips head screw driver and gently force the prongs open a little until you have a snug fit.