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.