They were a simple concept: a magazine filled with X-rated photos, usually outtakes from porn films, sold as fantasy material to enhance your masturbatory experience. They were mostly wall-to-wall photos and almost no text.
Stroke mags often had a simple theme around which the photos were organized: blowjobs, threeways, outdoor sex, leather sex, you name it. Seen here are photos from a stroke mag called Phallic Fantasies, which is packed with cock shots -- some closeups, some showing the bloke to whom the meat belongs.
When I was an unattached lad and couldn't get any action on a particular evening, I would retire to bed with a stroke mag, thumb through the photos for a few minutes, then turn out the lights and have at it with my right hand while my brain built the necessary fantasy. Once I shot my load, I then fell asleep. I'm sure I'm not the only one who did this.
If you'd like to download a free folder with scans of the entire magazine, please click here or here.