Serial connections can be confusing and are even more so when you try to connect devices to the older Apple Macintosh computers. However, you can trust Monoprice to have the cables you need for almost any situation!
The Macintosh Plus (Mac+) used an 8-pin mini-DIN connector for it's serial output, which used the balanced RS-422 interface, instead of the more common RS-232. Meanwhile, the original Apple ImageWriter I printer used a 25-pin RS-232 interface.
This cable connects the Mac+ printer output port to the ImageWriter I's DB-25 RS-232 input. It has molded plugs and the DB-25 end has thumbscrews to secure it to the printer.