The pneumatic measuring gauge is an assembly, which when paired with the correct attachments, makes measuring the air pressure inside a pneumatic spear gun easy even during pumping. This allows a precise pressure measurement with less wasted energy ensuring you have consistent air pressure in your gun. The gauge by itself will measure the pressure in an Omersub pneumatic spear gun. To measure the pressure in a Mares pneumatic spear gun add adapter OSBAPAMK. To measure the pressure in a Cressi Sub pneumatic spear gun add adapter OSBAPACK.