The Impact Band slipped on my iPhone 4 easily. Though it's made of a tough material, you can stretch it slightly. When it's on, the Impact Band adds a decent amount of girth to my handset, but the payback is a comfortably solid feel in my hand. I also liked that the rubbery material never felt that it would slip from my fingers. What's more, the Impact Band didn't result in a tighter fit in my pocket.
Though the iPhone's display and rear panels aren't protected, the Impact Band wraps around either side to offer some protection. There are gaps in the band for the docking port, the speaker and microphone, the headset jack, and the ringer switch. You can access the ringer switch easily, but the hole around the headset jack could be larger. It's not an issue if you're using Apple's standard wired headset, but you may have trouble fitting a nonregulation headset. Also, I had to press quite firmly to activate the volume bottoms with the band on.
I used the Impact Band for several days with my iPhone 4. I'm a natural klutz, so it's pretty much guaranteed that I'll drop my phone at least once a day. Fortunately, the Impact Band held up to the torture. When dropped on a carpet, a sidewalk, and or a hardwood floor (only the first one was an accident) the iPhone emerged unscathed. I also fumbled with it on a table and didn't have a problem. Since the rear of the phone isn't covered, the Impact Band won't offer protection if you drop your phone on an uneven surface like a rocky stream bed. That's one test I didn't attempt.
Out of all the cases I saw at CTIA 2012, Tech21's products were the only ones to make it on our Best of CTIA list. Indeed, the Impact Band delivers on Tech21's promises for a sturdy case that will protect your iPhone without being too big or ugly. At $39.99 it is expensive, and I'd tweak the design a bit, but for most tumbles and falls, the Impact Band and D30 do their jobs.