http://www.drsfostersmith.com/product/NavResults.cfm?Ntt=feliway&Ntk=All&Ntx=mod
e+matchallpartial&Np=1&N=2002

it supposedly a "happy cat" pheromone, used to calm easily-agitated cats,
and helps to stop them from clawing/peeing in the wrong places.

I used them with my 7, but it made one of them very paranoid, like he could
smell a strange cat & couldn't find it, so he was afraid that it was going
to attack him, therefore he stayed in the 'office' where with his food dish,
rarely coming out and hardly playing or interacting with the other 6.  I got
rid of the diffusers & he is a happy cat himself, now, actually playing with
toys again, and chasing & playing with the others (providing that they too
are in the mood for play).