How can you the difference between an iphone 3g and an iphone 3gs?

I bought a screen for the iphone 3gs then i realized i have the iphone 3g. Some of the reviews said that they recieved an iphone 3g screen and some said they recieved an iphone 3gs screen. Do you know how to tell the difference? and will an iphone 3gs fit on an iphone 3g|||Yes there is a difference between the iPhone 3G screen/digitizer and the iPhone 3Gs screen/digitizer. The glass is the same but the cable for the digitizer connection is not. You will be able to tell the that the connection is different once you open the iPhone. The 3Gs connector has a wider tab in the middle and will not fit. If you want someone to come out to your home or business and replace the screen for you visit http://www.techlifemobile.net and schedule a appointment.|||Your not very specific with you question you mean a screen protector? Both screens are the same it's just the 3GS has more speed to it than the 3G an the writing on the backs different that's all