This is our new design hose adapter to fit in a coolant hose with ID of 38mm to measure the presence of coolant in the hose as well as a port to fit a coolant temperature probe for temperature measurement - This adapter is used on most Japanese engines or any other engine that does not have a plastic pressurized header tank. The hose is fitted to the top coolant hose. NOTE: Supplied WITHOUT the temperature sender - please purchase separately.