There are two types. Short ram and Cold Air Intake (CAI)
CAIs are better because they pull in cooler air from outside the engine compartment. Depending on the application you can also get a bid of a ram air effect going down the highway. The only problem with them is that they can allow water into the engine if you drive in a flooded area or really heavy rain.
the ice box is best. Gives you benefit of a cold air source from the cai, mid-high gains from the short ram, doesnt suck in water, really quiet for sleeper, and loud when you take off the top cap. Its the best of both worlds.
* i bought a "type r" version of it. I am pretty sure it is generic. i got it for 75 with a filter, kinda pricey but i think its worth it. had to take off bumper to install but well worth it if you live in CA. You can't really hear the moded intake with cap on.