Direct from the Manufacturer - USA SenSafe Ida’s Iron Test , (Fe+2) #481046. CONTAINS 1 BOTTLE OF 25 TEST STRIPS FOR MEASURING IRON LEVELS IN WATER. If low range detection of dissolved Iron (Fe+2) is what you need, then SenSafe Ida’s Iron Check is the answer. SenSafe Ida’s Iron Check is designed to specifically react with Iron, without interference from other heavy metals that may be present. Say goodbye to dangerous, time-consuming wet-chemical kits that require extensive training. This patented test is a simple dip-and-read test procedure that requires no technical training. Simply dip one strip into the water for 30 seconds with a back-and-forth motion, remove the strip, wait 15 seconds for the color to develop, and match with the closest color match to determine your concentration of Iron. Note: This test detects dissolved Iron (Fe+2). For best results, run test immediately after collecting a fresh water sample. If "rust" is visible, the Iron has oxidized to Fe+3 so you need a Total Iron test (see WaterWorks Total Iron #481623-V). This product DOES NOT require an eXact photometer to read results.