Note: You cannot add to RFID locks directly. You must write data into by a 125kHz RFID card writer use. They are blank tags, no data inside.Sensing Distance: 2.5 to 10 cm (1 to 4 inch); Data Storage Life: 10 Years.Writable & RewritableFrequency: 125 KHzChip type: T5577Type: Read and rewrite key tagsWaterproof: Water resistantColour: blueMaterial: ABSSize: about 27.5 x 35 x 4mmPackage Contents:50 x Writable 125kHz RFID Key FobOnly the above package content, other products are not included.Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.