Measurement items: Residual chlorine (free / DPD method); Number of measures: 50; Simple water quality inspection tool; Measurement principle: DPD ratio color; Measurement scale: 0.1, 0.2, 0.4, 1, 2, 5 mg/L. Measurement time: 10 seconds; Contents: 50 tubes (5 laminating bags of 10 bags), storage bag, standard color (Case Included) 1 Piece, 1 Usage