This is a Professional Grade Hydrometer Set for making maple syrup. Made proudly in the USA. These instruments are non-toxic with heavy walled glass, easy to read scales, and are N.I.S.T traceable! This Kit includes (4) Precision Hydrometers packed in a Custom Instrument Case. Single hydrometers are available, call (717) 453-7171 Monday thru Thursday 7:00 a.m. to 5:00 p.m. and we can help.