COMBO PACK! Hanna Instruments HI721 Iron Checker HC Handheld Colorimeter 0.00 to 5.00 ppm Range plus (1) HI 721-25 (25 reagents) Device can be calibrated with water, without purchasing additional solutions Single button operation for ease of use Uses EPA Phenantroline method 315, a reaction that causes an orange tint in the sample Auto-off function to extend battery life. Large LCD screen for readability HI 721-25 (25 extra reagents)