What is the difference between ( )FLZ-(R)SM1-TB and ( )FLZ-(R)SM2-TB(LF)(SN)?

The difference is the material to conform to RoHS compliance.

The older SM1 / RSM1 are of 46 Nylon.
The compliant SM2 / RSM2 are of Glass-filled PA6T Nylon. These better withstand the higher temperatures required for the lead free solder reflow process.

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