Our sim cards are with the AT&T mobile network - America's largest nationwide mobile network, servicing the USA, Hawaii, the US Virgin Islands and Puerto Rico and giving voice, SMS and 3G/4G data. AT&T is America's most reliable network and covers more than 99% of America's population
(Source: http://www.att.com/network/en/index.html?utm_medium=email&utm_campaign=Winback&source=ECQT0000060V01V9E)
Data speeds vary depending on your device, local congestion, distance from cell tower etc. However your data speeds will be similar to the Telstra, Optus or Vodafone network in Australia.
Check below for some videos of speed tests conducted on an Australian iPhone 6 using a sim card from www.usaprepaidsimcard.com.au:
New York City speed test
Omaha, Nebraska speed test
