Milwaukee pH Replacement Electrode for pH55 or pH56The Milwaukee MI56P is the replacement pH temperature probe for the pH55 and pH56 PRO Testers (sold separately). The MI56P measures pH and temperature and easily slides into the tester fitting then screws into the meter body for secure installation. California Proposition 65 Proposition 65 Warning: This product can expose you to chemicals that are known to the State of California to cause cancer and birth defects or other reproductive harm.