NACS, or Neptune Adjustable Communication Support is a Patented OCEAN REEF accessory used to mount your O.R. communication device to your IDM. It’s light, sturdy and durable. It distributes the weight of the comm unit perfectly to the point you don’t even feel it anymore. This model now features the possibility to fold inside the mask when storing the IDM. Compatible with left ear type comm. units, such as the GSM G.divers.