Are there different hardware versions of the iPhone 4S?

Yes! there are two distinct versions, as the cell networks use different technologies which require differences. This is no different than any other cellphone maker that offer CDMA & GSM phones.

The guts are different and the cases them selves are slightly different (antenna & SIM slot). The IOS GUI, Apps and the controls are the all same (just minor control settings differences).

Make sure you get the correct one for the cell network you'll be accessing.

A CDMA iPhone (Verizon) does not have a SIM.

It does not have a SIM slot on the side of the phone either.

So there is 1 difference that makes for 2 different hardware

iPhone chassis/cases.

The answers on this post are all wrong.

The original question was about the 4S and the answers given were for the 4.

For the iphone 4 there is no sim for sprint. For the 4S there is. I just tore one down and replaced the screen yesterday. It had a sim.

The hardware SEEMS to be exactly the same. The part of the phone that utilizes CDMA or GSM is a chipset on the motherboard itself. Not in the internal midframe assembly.

Ok I get how he put it now. Brad is correct.

Actually there are hardware differences between US/global and EU versions. The top antenna is tuned differently, possibly to comply with local RF standards. Otherwise they are pretty much the same. The BOM option list has 9 entries: GU US/ GUC US/ GU EU. Each with 3 sub models of different storage capacity. These are very subtle differences, I didn't notice until recently.

As for the GU and GUC differences, they share the same hardware but with different burnt-in programming. The GUC ones are provisioned with MEIDs to work on CDMA networks while GU ones are just regular GSM/UMTS phones. These are supposedly software controlled but done in the factory with low level direct programming. Not possible to change outside the factory or it is even meant to be permanent

I know this is an old post but its one of the top google results so I thought I'd chime in. I have replaced dozens of iPhone 4S screens, batteries, back covers, buttons and charging/data ports and was thrown for a loop when I found a new hard frame type today. The standard iPhone 4S replacement screen did required modification to make it fit (by that I mean cutting off screen anchors). Just an FYI in case your newly purchased screen doesn't fit.