Metcal STTC Soldering Cartridges for MX Series. STTC Cartridges provide a wide range of options for through-hole and SMD Rework. STTC soldering cartridges for MX-catrtridges series For use with the MX-500/ -5000/ -5200 systems and MX-RM3E and MX-H1-AV hand-pieces