PH Combined Electrode with Glass Body Model 65-IP 65-IIP Measuring Range 0 - 14 pH Temperature Range 0 - 60 °C Zero point value 7 +/- 1 pH Junction Ceramic Reference Cell Ag/Agcl, KCL solution refillable Ag/Agcl, KCL gel Size dia.12 x length 140 mm Plug BNC + 1 m cable 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. http://yingming.17.cn/product_17006.html