To expand on clembo's answer, you can find more information about the Instant AP products here:
http://www.arubanetworks.com/products/instant-access-points
This page will tell you what IAP's are available and tell you about their features.
The IAP models are the same as the standard AP's but with different firmware, so they look the same and have the same features.
Just remember, like clembo said. the model numbers must begin with IAP, not AP :)