A band, including an extendable loop and worn around a user’s arm, is used to apply a compressive force to an attacker’s neck in self-defense. Top end of the displaceable button is formed with a notch in which the free end of the lock hook is restricted in a locked state. A first antenna is supported by the circuit board within the housing and operatively connected to the RF circuitry and configured for cellular phone communications. The resulting polymers are also described.