Contains 1 mL each of these mixtures. 31804: Caffeine (caffeine at 5 µg/mL in water) 31803: Caffeine (caffeine at 25 µg/mL in water) 31802: Caffeine (caffeine at 125 µg/mL in water) 31801: Caffeine (caffeine at 250 µg/mL in water) 31800: Caffeine (caffeine at 500 µg/mL in water)