I've actually got a couple of these from this very online shop. I had one for my iphone 4 and one for my samsung galaxy s2 (that i replaced my iphone 4 with)

Yes it does work with an unlocked iphone 4. I had no problems with it at all on the iphone 4 and use the 28th gen plus no-cut on my samsung galaxy s2 daily.

I find it really useful and couldn't go back to the days of long-winded sim switching.

So yea, if anyone's wondering if it does work, i can confirm that it does.