Note: You can not add them to RFID locks directly. You must write records into them through a 125kHz RFID card publisher use. They are clear tags, no information inside. Sensing Distance: 2 to 10 cm (1 to four inch); Data Storage Life: 10 Years & Rewritable Frequency: one hundred twenty five KHz Chip type: T5577 Type: Read and rewrite key tags Waterproof: Water resistant Colour: blue Material: ABS Size: about 27 x 35 x 4mm Package Contents: 50 x Writable 125kHz RFID Key Fob Only the above package content, different item will not be included. Note: Light and assorted reveals can cause the colour of the item within the picture slightly varied from the real thing. The dimension allowed error is +/- 1-3cm.