Sinomeasure standard pH calibration solutions have an accuracy of +/- 0.01 pH at 25°C (77°F). Sinomeasure can provide the most popular and commonly used buffers (4.00, 7.00, 10.00 and 4.00, 6.86, 9.18) and which are dyed different colors so they can be easily identified when you are busy working. Features Accuracy: +/- 0.01 pH at 25°C (77°F)Solution value: 4.00, 7.00, 10.00 and 4.00, 6.86, 9.18Volume: 50ml * 3