If you dont know why this is a good offer (other than it’s freebie)
The xSLX uses ISO15963 which isn’t as common as ISO14443A but there are some things it works well with
My Spark (original) which is also ISO15963 it is probaly my best xSeries as far as read range.
If I didn’t have the Spark, I would grab an xSLX just to have my bases covered, and the fact you can get it for free, is a no brainer