Replacement sensor probes for the LPHT1-Plus series water quality pens (listed separately as the LPHT1-Plus Series Multiparameter Water Quality Pen): pH sensor (PH1-S type) for LPHT1-Plus / LPCT1-Plus, ORP sensor (ORP1-S type) for LPORPT1-Plus / LPCT1-Plus, and conductivity sensor (EC1-S type) for LPECT1-Plus / LPCT1-Plus. Per-sensor details are listed in the comparison table below.