I have strips that I got from the builder when starting up my pool. Drop kit I found at the local Leslies for about $20, and a waterproof meter with 3000 ppm calibration solution I got from E-bay for about $50. The are all within about 100 ppm of each other. The Meter is by far the easiest, but I haven't had it long enough to know if the calibration holds well. The drops are a bit freaky to use (solids preciptate out etc.), but the color change is VERY clear. Resolution on my kit is 200 PPM. Strips are still accurate after 2 years, but are annoyingly slow to use. They all work well enough to figure out how much salt to add