The link the guy posted in the previous reply, you aren't guaranteed the right color. With the ones from Radtech, you're guaranteed a set of matching black or white.
I was concerned at first that the headphone jack protector wouldn't fit the iPhone 4 since it appears a little tapered to match the contour of the 3G/3GS, but it fits perfectly. In fact, the tapered side gives you a little something to grab onto when you're pulling it out.
The 30-pin port plug works fine with the Apple bumper too btw. The headphone plug does also, but it's basically impossible to remove without taking the bumper off first. This isn't a concern for me because I use bluetooth headphones almost exclusively.