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. 18 pack ph calibration packets: 6*ph 6.86 packets, 6*ph 4.00 packets, 6*ph 9.18 packets, cost-effective and flexible for using. Color: As shown Material: Plastic type: 6.86/4.01/9.18 Package Contents: 18*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.