Would you have to use a micro sim card on an iPhone 4S/5?

I have the iPhone 5 and my friend has the iPhone 4S (both unlocked) we're going to get them through a net10 sim card could we just get the regular sim card or would we have to get a micro sim card

Yes, but you can get a sim cutter which can make a regular sim a micro one, its very useful!

Yes a micro sim. You can buy a sim cutter from clove technology for £5 and it comes with adapters so you can put the sim in a standard sim phone after its been cut should you need to.

If you have a iphone 5? Then you are gonna need a Nano sim card and your friend would need the micro for the 4s.