The 1.5SMC24CA: This makes it a fit for protecting 24 V DC buses, telecom supplies, or automotive load-dump transients where the steady-state rail stays under 20.5 V.
The large tab area under the cathode (for unidirectional variants) or the body itself (bidirectional) conducts heat into the board — the 1500 W pulse rating assumes a low-thermal-resistance layout with adequate copper pour. The wide range means the clamping voltage and leakage current stay within datasheet limits across the full temperature band, though leakage at 150°C will be higher than at 25°C — a consideration for high-impedance circuits.