Current jointing fittings are made of the same or similar materials as the bonded conductor with suitable physical properties with respect to current transfer and electrochemical interaction between the conductor and the fitting.
Relative transition resistance of the coupling must be less than the relative resistance of the conductor for which the conductor is intended. When joining conductors of different cross-sections or materials, the measured values must be transferred to a smaller cross-section or to a material with lower conductivity. Current fittings must have a warming smaller than the largest wire for which the fitting is intended. When jointing different cross-sections of cables, the cable temperature of the conductor is equal to the temperature of the cable with the lowest temperature.