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