The H-58X (3, 4, 5, 7, 9), H-108X (3, 4, 5, 7, 9), and H-208X (3, 5) are Pilot’s classic drafting family from the 1980s.
The H-56X (3, 4, 5, 7, 9) and H-109X (3, 4, 5, 7, 9) make up Pilot’s alternative drafting family.
You can expect to pay the most for the 0.4 in each set, with the H-584 and H-1084 being particularly hard to find.
If you ever see a complete set of 5 for sale—with stickers—you should probably just get it. When I started collecting, the entire H-109X family was available for $210, but I was too stupid to jump on the deal. Same thing would cost at least $350 to put together now, if not more.
Pilot has plenty of other drafting pencils, but I consider all except the double-knocks (hi-mecha) to be precursors to the series mentioned above (think 1970s vs. 1980s).
Two other drafting outliers exist—the knurled ring ¥800 pieces (3 & 5, red & green & yellow rings) and the first generation Pilot drafter with lead hardness indicator window (red and white specimens in the lower left corner; I’ve seen black, white, and red in 3 and 5).