Features and Benefits:

• Most heavy duty engine (Class 7-8 trucks)
  manufacturers, have chosen to utilize SCR. This
  Includes Detroit Diesel (DD13, DD15, and DD16
  models), Cummins (ISX line), PACCAR, and Volvo/Mack
• SCR-equipped engines require the periodic addition
  of Diesel Exhaust Fluid (DEF, a urea solution) to enable
  the process. DEF is available in a bottle at most truck
  stops, and some have installed bulk DEF dispensers
  near the Diesel Fuel pumps. However, to ensure the
  proper operation of the SCR system, operators must
  ensure the DEF in their vehicle consists of a 32.5%
  Urea / Water solution
• Simplify DEF testing!
• Features digital display
• Easy-to-read, quick and accurate
• Measures UREA concentration and displays on screen
• Displays washer fluid freeze point

Electronic DEF tester (refractometer) - Measures the concrentration in % of the UREA in DEF fluid for diesel exhaust aftertreatment systems. Also measures freeze point (in deg. F) of washer fluid in the same device.