This buffer solution comes in powder form, so it's lightweight, takes up very little space, is inexpensive and has an indefinite shelf life. FEATURES: Variety pack of ORP buffer solution; test kit to check the quality of your ORP electrode; simple to use; powder has an indefinite shelf life. SPECIFICATIONS: Total volume: 1.0 liter; each powder packet makes 100 ml of solution (when mixed with distilled or deionized water). CONTENTS: 5 packets of 92mV, 5 packets of 265mV. EXTRAS: Includes 3 empty 100 ml bottles. ACCURACY: /- 0.2 ORP at 25 degrees C. Preparation directions included with the kit.