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How to copy a key fob
Purchase an rfid writer online.
An rfid writer is capable of reading and writing 125khz key fobs. Search online for an rfid writer and reader and purchase one that has good user reviews.
Some rfid handheld readers and writers will come with blank key fobs that you can use to make a copy. 125khz key fobs are commonly used to lock doors in office buildings and apartment complexes.