Does the job,
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This review is from: New iPhone 5 Nano Sim cutter - G-HUB Dual Head Sim Cutter for use with Standard AND Micro Sim card conversion to New Nano Sim size for Apple iPhone 5 (Includes 2 converter adapters) (Electronics)
It's a sim cutter reducing an existing sim (not standard sim) to that of a nano sim.
Be careful though. Mine didn't come with the shown metal templates so had to work around it.