The Iron Bands of Bilarro are an enchanted metal sphere that originally appeared in an unpublished 1974 adventure module by Robert J. Kuntz (entitled "the Orc Level). They were later added to the Dungeons & Dragons series of role-playing games (first appearing in Unearthed Arcana).
The Iron Bands appear as a small (usually rusted) sphere of metal. It appears to be constructed of many bands of metal that are tightly fit together. The sphere will often have a word or phrase engraved into it, but you will usually have to clear off the rust to find it (but the rust will inevitably return within a few months).
If the sphere is thrown at a creature (and the command word spoken), it can capture a creature up to 20 feet in height. When tossed the individual pieces that make up the sphere expand with a metallic sound, and wrap themselves around the target, immobilizing the creature. This is quite a horrific sight for the target, as it sort of resembles a giant spider in flight towards them.
These spheres radiate magic of an unknown nature, but spheres of technological (as opposed to magical), origin are possible as well. The first reported use of this item was by the semi-mythical Robilar in capturing his foes, but it is not known if he was the one who actually first created the item. The name was later transposed to "Bilarro", and that name seems to have stuck.
This would also be a fantastic item to place into a horror movie (I am specifically thinking about a movie called Phantasm which had flying metal spheres that had various attachements, they would hunt down and kill people), the special effects alone would make it worth writing one of these into a movie.
This is only my interpretation of this item, which is based largely upon its use in the older versions of the Dungeons & Dragons series of games. Your set of Iron Bands of Bilarro may be totally different, so always be sure and read the instructions.