Here's one installed on an 11.5" barrel...
They are only .5" longer then the real deal (4.8" overall). They spread that 1/2" around so that it doesn't look too out of proportion (little bit extra at the wrench flat area, little extra in the body, and a little extra in the slots).
I really prefer the look of the ar15sport version than a 4.3" original length moderator on a longer barrel.