Huawei E3531 offers dual-band UMTS (900/2100 MHz) and quad-band GSM (850/900/1800/1900 MHz). The HUAWEI E3531 is SIM card unlocked and free for any operators. So the E3531 modem could be used in most countries in Europe, but only in the U.S. and parts of Asia, the HUAWEI E3531 can’t be used. With dimensions of 84x27x10, 5 mm, and weight of only 30 grams, the E3531 stick is very compact and slim, which makes it eas to take in hand or pocket when travelling. Huawei E3531 has a connector for an external antenna, it helps user to get better signal strength in rural area where lower signal.