2 Tekin Gold Plated High Power 5mm to 4mm Bullet Connector Reducers. 5mm bullets on your battery packs but 4mm charge and ESC leads? No problem with these reducers, just pop them in your battery and 5mm becomes 4mm. Bullet connectors provide a solid connection with reduced resistance compared to other styles of connectors. Don't leave power on the table, harness it all with quality solid connectors and FlexWire!