Waterproof and high temperature and high sensitivity, rugged, never rust, corrosion; resistant to heat Anti-variant; sealing strong for security patrol, sauna door locks,electronic door locks, door intercom, card systems, identification, banking, Communications, rail transportation, transportation, and so many fields Information ibutton RW1990 memory 64, can be repeated rubbing, write the diy code. mainly used in Russia, Europe and Turkey and west Asia countries RW1990 - f5 can change code can copy, 64 k memory read/write IButton. Compatible DS1990a Specification: 16.25 mm (diameter) x 5.89 mm (high) Colour: random color, don't accept the specified color Material: ABS Package Contents: 100 x ID token keychain Only 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.