8mm loops were the sexual underground. They were sold under the counter in adult bookstores or by shady peddlers and selling or possessing them was a crime back in the day. The loops usually came in white boxes: b&w was one price, color was a higher price. A film like this could cost $20 to $100 per loop...and that's '60s and '70s money! And you never knew what you were getting. Later the loops would be labeled with names like "Pretty Girls," "Golden Girls," etc. Most of these loops had no titles as after repeated playing the film would get worn and simply break off: they would just start with hardcore sex or get down to it after a minute or so of plot. Common plots were doctor/patient, boss/secretary, hitchhikers being picked up, etc., with darker plots showcasing hardcore S&M, bondage, rape and other twisted shit. Some recognizable stars appeared in these things, too.