This is the Ofna Micro Fail Safe Unit for glow powered cars.

FEATURES: CPU fuzzy logic system with low battery warning
Prevents accidents by detecting low battery voltage, low radio
battery voltage, no radio signal, and signal interference
Stops vehicle by applying brake servo
Compatible with 4.8V-6V receiver power source

INCLUDES: One fail safe with Futaba J connectors

REQUIRES: Connecting fail-safe unit to throttle/brake servo and receiver

SPECS: Length: 7/8" (22mm)
Width: 5/8" (16mm)
Height: 1/4" (6mm)