Apera Instruments SX615 probe is the replacement probe for SX610 ph pen tester. This replacement probe is equipped with glass bulb membrane and built-in temperature sensor. It has a measurement range of -2.00 to 16.00 ph and 0 to 50˚c. Its 8 mm diameter probe allows measurement in most test tubes, making it perfect for educational use and other common aqueous solution's ph measurement, such as hydroponics, aquaculture, pool & spas, water treatment, environmental monitoring, etc. The product is CE and RoHS certified, and is manufactured under an ISO 9001:2015 certified quality system.