For most sea, the salinty is between 30‰~35‰. So this refractometer is ideal for simple marine monitoring and research.
Ideal for lab and indurstry use for testing salinity solution in the range of 0~100‰.
If you use a salt chlorine machine to disinfect your pool, you should make sure the salinity right first, normally the salinity should be between 3‰~7‰, this refractometer can help.
Ideal for aquariums or marine fishkeeping amateurs, cause they just need to make the salinity of water similar to the sea water.