PH Combined Electrode with Glass Body Note: Difference between the two models is the reference cell electrolyte. 65-IP is with solution form and can be refilled. 65-IIP is in gel form which last life time, not need to refill. I am the manufacturer of the YM Instrument Co.Ltd in China. Our products are mainly focus on pH tester, Nutra Wand conductivity meters, mini TDS meters such as EC, CF, ppm, ppt, uS/cm, mS/cm testers. pH combined electrodes, skin electrodes, Dissolved Oxygen (DO) electrodes, Conductivity and ORP electrodes. related fields. Our product advances are mainly in the prices and quality fields. We can provide you with good quality and low price Show More