When people get a set of keys they normally attach it to something to put it with whether it was a lanyard or it is a key chain. The little decoration attached to a key chain is a ‘fob’ in English, which is known as брелок in Russian. According to most standard dictionaries this is how this word declines:

Those are the little charms or trinkets that a person can use to accessorize their keys and help keep a better track of them. There are ones for both ones for men and women. Guys normally choose ones such as bottle openers or more masculine ones where as girls have more options such as teddy bears, butterflies, or hearts. Personally I have cartoon characters. There are also ones that you can use to show support for things such as the support ribbons or national ones. Holidays have their own key chains or ones from movies. They make good gifts for little kids or friends. My friend for one Christmas got our group of friends all matching ones.There are two declensions of брелок because there is the formal form and the colloquial form.

Don comments: The word брелок is actually undergoing a shift in Russian. Originally the word was borrowed from French breloque, and in the sense of a pendant or decoration that hangs from a bracelet or pocket watch, it always declined like this:

	Sg	Pl
Nom	брелок	брелоки
Acc	брелок	брелоки
Gen	брелока	брелоков
Pre	брелоке	брелоках
Dat	брелоку	брелокам
Ins	брелоком	брелоками

Nowadays almost no one has a pocket watch, much less one with a decoration, so the word is very commonly used to mean a fob on a key chain. In that sense the declension that Janell mentioned is much more common. There is a nice discussion of the issue at rg.ru (mirror). My own advice at this stage would be to use the new declension in conversation, and the old version in professional writing.