Suitable with most of pH meters, perfect Calibrating. pH buffer calibration solution powder accuracy is ±0.01pH, accurate and precise. Individually wrapped to maintain freshness until use. Made with qualify materia. Easy to use: Mix the buffer powder with 250ML distilled water, put the pH meter in the solution and gently stir and wait a few seconds for the result. 90 pack ph calibration packets: 30 x ph 6.86 packets, 30 x ph 4.00 packets, 30 x ph 9.18 packets, cost-effective and flexible for using. Color: As shown Material: Plastic type: 6.86/4.01/9.18 Package Contents: 90 x pH buffer Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.