This is the Traxxas Antenna Cap Set with Antenna Spool. The antenna spool is used for wrapping excess antenna wire before inserting it in the antenna tube to prevent wire from hanging out the end of the tube, preventing damaged antenna wires caused by rollovers.
This is the Traxxas Black Antenna Tube with Cap and Wire Retainer. These are compatible with nearly all Traxxas cars, trucks and boats. The sleek black design looks great as well.