Are you having trouble using your old Sim card to fit for your Iphone 4 and Ipad?
Basically Iphone 4 and Ipad is using Micro Sim Cards to minimize the size of your Sim Card. All you have to do is to trim or cut your sim to fit on your Iphone 4 and Ipad.
Well this would solve your problem, Micro Sim Card Cutter + 2x MicroSim Adapter For iPhone 4 & iPad is the best web product to solve that problem.
This best sim card cutter for iphone and ipad works like a paper puncher and would look like this picture below.

Iphone 4 and ipad sim card cutter
This package would include 2 adapters for Iphone4 and Ipad.
This is the best price I have canvassed online for Sim Card cutter for Micro Sim.
Testimonial
Used this product on many SIM cards to test it out.
Cuts out the chip portion as it should. NOT all SIM cards are the same.
Some are created with the chip are bigger than others.
You can expect it cut out the SIM cards perfectly and the same size all the time.
However you HAVE to expect the SIM card chip to be effected if it extends outside of the cutting area.
Keep the outer area of the SIM card that you cut. You will never know when you will need them.
The micro SIM adapters that come with this cutter are a little thicker than the SIMs.
Tried to use the adapter, with a micro SIM inside, in a Motorola SLVR L7 and it was more of a chore than their worth to get the adapter latched in. Do NOT use these adapters with iPhone 3G/S type SIM trays. There will be a possible chance it will be jammed in.
I am giving the micro SIM cutter five stars and ignoring the adapters.
Andrew-
This product really works. At first I thought it would break the whole sim card but after I punched it then places the micro sim in the adapter, it works very well.
Mike-