Ideal for use with the ZeroNoise Pit-Link GSM communication system this helmet kit is designed for circuit use and fits full face helmets. The kit comprises of a dynamic noise cancelling microphone for superb sound clarity. Foam spacing discs are included to obtain the optimum microphone position.Dynamic noise cancelling microphone for optimum soundIncludes provision to connect earplug speakers with a choice of connectorDesigned to fit full face helmetsThe helmet kit connects to the amplifier via an option of 4 or 5 pin male Nexus plug. The 4 pin option is the correct type for use with the ZeroNoise Pit-Link GSM communication system.