Fasarta technology was an important high-tech luxury item in the home timeline. Everyone who was anyone owned a fasarta. The subflexive fasarta was the best kind.
When Gianfranco Mazzilli visited the home timeline, he was bewildered by the numerous advertisements for various consumer products such as cars, cologne, fasartas and soda. His own alternate did not have such ads, and he did not even know what a fasarta was. However, he did not ask about that, not wanting to seem ignorant.
One of the hardships which Crosstime operatives had to face in alternates was to do without the use of a fasarta for the duration of their mission. Though operatives could maintain a secret room or basement where home timeline artifacts were kept, they were not allowed to have a fasarta among these artifacts. The rule was less strict for alternates where there were no local human beings and people from home could move freely. When Justin Monroe had to undergo quarantine after being in the alternate where Ohio used a tailored measles against Virginia, he found that facilities in the quarantine alternate did include a bare-bones fasarta. During his three weeks there, he let that fasarta pamper him a little bit, as much as it could, while waiting impatiently to return to the home timeline and the much better fasartas available there.
The repeated references to a "fasarta" without defining what it is, is a running gag throughout the Crosstime series. See also Literary Allusions in Turtledove's Work#Robert A. Heinlein.