From CORE RC are these Lockdown Heatsink Bullet Plug Grips. A tight and reliable connection between your LiPo and speed control eliminates any losses of power, increased resistance, arcing and general poor electronic set up. Giving a reliable connection with an easy twist of the attractive looking locking screw. Easy to identify Red +ve and Black -ve plugs helps prevent cross connection and that moment every racer dreads, the magic smoke escaping from your speed control ! 4mm Size.