If I were starting over, and buying a single tool to sharpen my knives, this is what I would get. It has a medium (600) surface on one side and a fine (1800) surface on the other. It's 4" long, 1 1/4" wide, and less than 1/16" thick (.055"). The plate and it's plastic sleeve weigh about 1 1/4 ounces. Made in the USA.
Also Great for sharpening scissors!
If I were going to add anything, I'd get something for a super fine finish or strop. On single sided plates (see below) I often glue a strip of 9 micron polishing film to the back of the single sided plate. On the two-sided plate you could probably glue it to plastic sleeve, or just keep it with the plate.