The Apera Instruments SX615 Replacement Probe is the replacement probe for SX610 pH Pen Testers. This replacement probe is equipped with a glass bulb membrane and built-in temperature sensor. The 10 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. CE-Certified and comes with a 6-month warranty