The MMSZ18T1G is a 18V Zener diode from ON Semiconductor, rated for 500mW power dissipation. It features ±5% tolerance and a surface mount SOD-123 package.
The MMSZ18ET1G is a 18V Zener diode from ON Semiconductor with 500mW power dissipation. Housed in a surface-mount SOD-123 package, it offers ±5% tolerance and 45Ω impedance.