Ensure your pH or conductivity/TDS instruments operate with maximum accuracy. Choose from a wide range of pH, conductivity and TDS calibration standards. All conductivity solutions have conversions to ppm.All solutions are premixed and rigorously tested to give dependable performance. Reagents are standardized to NIST references. pH Buffers have ۪.01 accuracy at 25°C. Each bottle has a safety-sealed cap and is double packaged. Pint (460 mL) bottles measure 7-3/8"H x 2-1/2" dia. Shelf life is one year unless opened. Bottles are recyclable. Oakton Singles have unquestionable reliability. Each pouch contains 20mL so there's no wasted material. Pouches are labeled with CAS numbers for product identification. Size: 4-1/2" x 5" x 4-1/2". Box of 20 pouches. Shipping weight = 1 lb. pHSingles include temperature correction tables. ۪.01pH at 25°C. TDSSingles have equivalent values for conductivity, ppm KCl, NaCl and 442 natural water TDS simulation. ۫% at 25°C.