This is the Hobbywing Xerun Super Capacitor Module [86030030].

This is a replacement Hobbywing Xerun Super Capacitor Module, intended for use with the Xerun series ESC's. 

Features:

• Super low impedance.
• Low temperature in working state.
• Reduces the RF interference to make the RC model more reliable,
• Improves the burst power when the motor starts to run.

Specifications:
Capacity: 330uF*2.
Voltage: 16V.
Impedance: 0.002 ohm
Ripple Current Endurance: 24 Amp
Size: 29mm * 13mm * 13.2mm
Weight: 5g
Suitable ESC: XERUN and EZRUN series 1/10 scale ESC.