This is the Sub Micro Servo included in the Two Speed Conversion Kit (TRAC4000) used on the Traxxas E-Maxx.

FEATURES:
Sub micro size, waterproof construction Actuates the Internal Shift Fork (TRAC3906) with the push of a
button from a 3-channel transmitter

INCLUDES:
Sub Micro Servo with universal connector

REQUIRES:
Installing at transmission and connecting to shift fork and receiver