This is the Sullivan Skywriter Smoke Pump.
 

FEATURES: Electronically controlled smoke pump for onboard smoke systems
          Ultrasonically sealed direct drive pump head
          Aluminum case
          Miniature microprocessor controlled electronic pulse drive flow
            control
          Smoke rate can be set with transmitter trim and mixed with the
            throttle channel
          Works with 6-12V battery packs

INCLUDES: One Sullivan Skywriter Smoke Pump

REQUIRES: Installing in model, connecting to smoke system and plugging into
            any unused receiver channel

SPECS:    Length: 3.8" (96mm)
          Width:  1.4" (36mm)
          Height: 1.4" (36mm)
          Weight: 3.9oz (109g)