OK, this is a point of discontention with me. I don't think you can easily group the rep numbers with size gains. I am a tall lifter, standing at 6'3 i have a harder time filling out then most. My 2 problem areas have been getting my shoulders to grow and my arms. I have always followed a 6-12 rep range workouts. This got me to deelop but slowly what i discovered shocked my when i did my usuall experiments in lifting.
I started doing lateral raises and curls with a lighter weight and do 1 set of non stop 100 reps. Sometomes i have to pause the set to let the blood rush back into a muscle for a few seconds, but the results are almost miraculous. My shoulders never get sore, in all my years they got sore maybe 3-4 times. Using the 100 rep method on only 1 set they have been growing and getting a nice soreness for weeks now. So in my experience mass or muscle building is a very multidimetional approach with reps ranging from 1-100. Incidentally 20 rep arm curls is what put 2 inches on my arms in the past.