The SM6T36A is a 600W unidirectional Zener TVS diode from STMicroelectronics. It features a 30.8V reverse standoff voltage and 64.3V clamping voltage in a surface-mount SMB package.
SM6T27A is a 600W Zener TVS diode from STMicroelectronics with 23.1V reverse standoff and 48.3V clamping voltage. It is surface mounted in a DO-214AA (SMB) package.