Used them once, found them in a box of stuff, don't plan on using them again. '2 mile' range on open clear ground, 3/4 in hilly, forested areas. I know an Airsoft guy who uses these, and he likes them.
14 Channel, runs on 3 AAs, they've got a jack for an earbud, but it's smaller than a normal headphone jack.
$15 shipped, obo.
here's an old review: http://jeepin.com/features/fr50/index.asp