Hanna Instrument HI775 Freshwater Alkalinity Checker Test Kit - Freshwater Aquariums FRESH WATER Alkalinity in 0 to 500 ppm Resolution: 1ppm Accuracy: 5ppm  5% of reading Max Temp Range: 0 to 50C (32 to 122F); RH max 95% non-condensing Dimensions: 81.5 x 61 x 37.5 mm (3.2 x 2.4 x 1.5) / Weight: 64 g (2.25 oz.)