Apera Instruments Salt20 Value Pocket Salinity Tester APERA's unique BPB (Brush-resistant Platinum Black) probe ensures high accuracy and consistency in a wide-range salinity measurement EASY Auto Calibration with auto buffer recognition; Auto Temp. Compensation (ATC) ensures accuracy in variant temperatures (0-50.0C) LARGE CLEAR LCD with DUAL Display of temp./ppt, and REMINDERS of completed calibrations and stable readings COMPLETE KIT with READY-TO-USE calibration solutions, batteries, and a lanyard in a portable carrying case 1000 hours' continuous operation time powered by AAA batteries