Compatible: Other universal tags like EM4100/4102 Not-compatible with encrypted: HID, Indala, Cobra, APCiK, Paradox, Radio, Honeywell, Kaba, Isonas, etc. Water resistant Can read and rewrite Each comes with Key ring included No external power required. Specfications: Color: Blue, Yellow, Red, Black, Green Size: 1.4*1.1*0.2 inch. Package included: 100 PCS (please choose the color you want)