The type I sell is a Bricor.
See:
http://www.bricor.com/
They are pricy (starting at $62) but top quality and in my mind the best on the market (which is why I carry them). Many people (myself included) who have tried them say they feel like a real shower, not like you are under dripping trees after a rainstorm - a common complaint about low-cost low-flow showerheads.