Compiled from 7 sources; we haven't tested these products ourselves yet. How we research
Quick answer
On published specs, uni Nano Dia is the best mechanical pencil lead for most people: 40 leads of 0.5 mm in ten grades from 4H to 4B for ¥220 (about US$1.40), blended with nano diamond for strength. Pentel Ain Stein is the ceramic-reinforced rival, Super Hi-Polymer the budget standard, and Pilot Color Eno the erasable colored lead.
On this page9 sections
The four lead tubes drawn in proportion with a 60 mm lead beside each, and a size chart from 0.2 to 1.3 mm at actual width (1 mm = 1.2 px).
uni Nano Dia mechanical pencil lead, 0.5 mm, 40 leads (uni0.5-202ND)uni
Japan
Not stated*
Price range: $under $5 per item
Pentel Ain Stein mechanical pencil lead, 0.5 mm, 40 leads (C275)Pentel
Japan
Not stated*
Price range: $under $5 per item
Pentel Super Hi-Polymer mechanical pencil lead, 0.5 mm, 12 gradesPentel
Japan
Japan*
Price range: $under $5 per item
Pilot Color Eno colored mechanical pencil lead, 0.7 mm, 10 leads, 8 colors (HRF7C-20)Pilot
Japan
Not stated*
Price range: $$$5–20 per item
Notes on these facts
uni Nano Dia mechanical pencil lead, 0.5 mm, 40 leads (uni0.5-202ND): Made by Mitsubishi Pencil Co., Ltd.. Country of manufacture not stated: Mitsubishi Pencil's pages we could reach and the Amazon US listings don't state where the standard black Nano Dia is made. Tacto Studio lists the related Nano Dia for Textbooks lead as made in Japan, but that is a different product, so we don't carry it over. Released: Mitsubishi Pencil describes the Nano Dia series as a long seller since 2008; we found no exact launch date.
Pentel Ain Stein mechanical pencil lead, 0.5 mm, 40 leads (C275): Made by ASTRUM Corporation (Tokyo), called Pentel Co., Ltd. until April 1, 2026; Pentel remains the brand. Country of manufacture not stated: None of the listings we read (Monk, Doublet, Cult Pens, Markers n Pens, Amazon) state where Ain Stein leads are made. Pentel's Japanese site no longer lists Ain Stein, and Pentel of America's 2022 and 2023 product catalogs, which give an origin for each product, don't include it. Pentel is a Japanese company, but that doesn't tell us the factory. Price: example listing.
Pentel Super Hi-Polymer mechanical pencil lead, 0.5 mm, 12 grades: Made by ASTRUM Corporation (Tokyo), called Pentel Co., Ltd. until April 1, 2026; Pentel remains the brand. Made in Japan: Pentel of America's 2022 product catalog, on its lead refills page, says "Country of Origin: Lead made in Japan." It doesn't say where the tubes are made, and Amazon and Pentel's US store don't state a country. Source.
Pilot Color Eno colored mechanical pencil lead, 0.7 mm, 10 leads, 8 colors (HRF7C-20): Made by Pilot Corporation (Japan); sold in the US by Pilot Corporation of America. Country of manufacture not stated: Pilot's Japanese web catalog pages for the Neox Color Eno lead and Color Eno pencil (read in full on October 22, 2026) and Amazon US don't state a country of manufacture. Check the tube.
Price bands are typical US retail, checked October 2026. Conversions to US dollars are approximate, at October 2026 rates (US$1 = ¥158 = ₩1,330 = NT$32.5 = CN¥6.7 = SEK 9.9 = DKK 6.7 = ₺49.6 = C$1.41 = A$1.43 = CZK 21.7; €1 = US$1.12; £1 = US$1.32; CHF 1 = US$1.21).
Key takeaways
Three of the four picks sit in our $ band (under $5 per tube); only the Pilot Color Eno, at ¥385 (about US$2.40) in Japan, reaches $$ ($5–20) in some US packs.
Nano Dia 0.5 mm comes in ten grades from 4H to 4B, 40 leads a case; Super Hi-Polymer 0.5 mm in twelve grades from 6H to 4B, per Pentel's catalog.
Pentel Ain Stein tubes hold 40 leads in 0.5 and 0.7 mm, 36 in 0.9 mm and 15 in 0.3 mm; in Japan the brand became Pentel Ain on January 30, 2023, at ¥220 (about US$1.40).
Super Hi-Polymer spans six sizes from 0.2 to 1.3 mm, and its 0.7 mm HB 3-pack ranked #1 in Amazon US mechanical pencil refills on October 22, 2026.
Every lead here is 60 mm (2.4 in) long, the standard that fits any pencil of the matching diameter.
What is the best mechanical pencil lead?
On published specs, uni Nano Dia is the best mechanical pencil lead for most people, with Pentel Ain Stein as the ceramic-reinforced rival, Super Hi-Polymer as the budget standard and Pilot Color Eno as the colored lead. Lead is cheap, so the choice is about size, grade and how often it breaks. Three picks sit in our $ band (under $5 per tube).
Nano Dia is #1 because it pairs ten grades in 0.5 mm with a nano-diamond blend for strength, at ¥220 (about US$1.40) a case. For the pencils, see best mechanical pencils.
Best overall:uni Nano Dia. Why it’s here: ten grades in 0.5 mm, 4H to 4B, blended with nano diamond for strength, 40 leads a case.
Best for heavy hands:Pentel Ain Stein. Why it’s here: the ceramic-reinforced rival, a porous structure Pentel says resists breaking; 40 leads of 0.5 mm, sold as Pentel Ain in Japan.
Best budget and most sizes:Pentel Super Hi-Polymer. Why it’s here: the most sizes here (six, 0.2 to 1.3 mm) and twelve 0.5 mm grades, and Amazon US’s best-selling refill.
Best colored lead:Pilot Color Eno. Why it’s here: the only colored lead here, 0.7 mm in 8 colors, wax-free so it erases; ¥385 (about US$2.40) for 10 leads.
How did we choose these picks?
We compiled these picks from published sources, not hands-on testing: makers’ Japanese spec pages and strength claims, retailer listings and Amazon US sales rank, US availability and price band. We haven’t run breakage tests, so we chose on sizes, grades, count and each maker’s published reinforcement.
How do the leads compare?
All four are 60 mm leads; they differ in sizes, grades and count. Figures come from each product’s guide.
uni Nano Dia
Pentel Ain Stein
Super Hi-Polymer
Pilot Color Eno
Sizes
0.3, 0.5, 0.7 mm (0.5 shown)
0.2 to 0.9 mm
0.2, 0.3, 0.5, 0.7, 0.9, 1.3 mm
0.7 mm
0.5 mm grades
10 (4H to 4B)
Multiple, HB to 2B most common
12 (6H to 4B)
Not applicable
Leads per tube
40
40 (0.5, 0.7), 36 (0.9), 15 (0.3)
8 to 30 by size
10
Lead length
60 mm (2.4 in)
60 mm (2.4 in)
60 mm (2.4 in)
60 mm (2.4 in)
Claim
Nano-diamond blend, harder to break
Ceramic cell structure, stronger
Standard polymer lead since 1960
Wax-free, erasable color
Made in
Not stated
Not stated
Japan
Not stated
Japan list price
¥220 (about US$1.40)
¥220 (about US$1.40) as Pentel Ain
¥110 (about US$0.70) for 16
¥385 (about US$2.40)
Band
$ (under $5)
$
$
$$ ($5–20)
Which lead size should you use?
0.5 mm unless you have a reason. It has the widest choice of grades and pencils. 0.3 mm suits small handwriting and drafting but snaps under pressure; 0.7 mm is the lead to switch to if you break 0.5 mm, and 0.9 mm and 1.3 mm suit sketching and children. Lead must match the pencil: a 0.5 mm pencil can’t take 0.7 mm lead.
Pentel’s Super Hi-Polymer is the only pick spanning 0.2 to 1.3 mm. The uni Kuru Toga, which rotates the lead as you write, has its own Kuru Toga lead, but standard 0.5 mm leads fit it too.
Which grade should you use?
HB for writing, B or 2B for darker notes, 2H and above for drafting. Pentel says HB matches a #2 pencil. Softer B grades write darker with less pressure but smudge more and wear faster; harder H grades stay sharp and light. Nano Dia’s ten 0.5 mm grades and Super Hi-Polymer’s twelve cover both ends.
Where are these leads made?
Japan, where stated. Pentel of America’s catalog gives Japan for Super Hi-Polymer. Mitsubishi Pencil, Pentel Japan and Pilot don’t print a country on the Nano Dia, Ain and Color Eno pages we read, so those read “Not stated” until the packaging settles it.
Frequently asked questions
What is the best lead for a mechanical pencil?
uni Nano Dia or Pentel Ain Stein for strength and a dark line; both are Japanese premium leads around ¥220 (about US$1.40) a tube and under $5 in the US. Super Hi-Polymer is the budget standard that most US pencils ship with, and it comes in the most sizes.
What size lead should I use?
0.5 mm is the all-round size with the most grades and the most pencils. Use 0.3 mm for tiny handwriting or technical drawing, 0.7 mm if you press hard or snap 0.5 mm leads, and 0.9 mm or above for sketching. The lead must match the pencil's diameter.
What do the lead grades mean?
H leads are harder and lighter, B leads softer and darker, with HB in the middle; Pentel says HB equals a #2 pencil. Nano Dia 0.5 mm runs 4H to 4B and Super Hi-Polymer 0.5 mm runs 6H to 4B. Most writers settle on HB or B.
Why does my lead keep breaking?
Usually too much lead showing, too much pressure or a thin size. Advance only a millimeter or two, try a 0.7 mm lead, or switch to a reinforced lead: Pentel says Ain Stein's ceramic structure resists breaking, and uni says Nano Dia's diamond blend does the same.
Is Ain Stein the same as Pentel Ain?
Pentel Ain is the Japanese successor. Pentel renewed its lead brand on January 30, 2023, the first change in 13 years, and sells it as Pentel Ain in Japan at ¥220 (about US$1.40). Ain Stein tubes continue in US and other export stock.
Can you get colored lead for a mechanical pencil?
Yes. Pilot Color Eno is 0.7 mm lead in 8 colors, 10 leads a tube, made without wax so it erases. uni also sells Nano Dia Color in 0.5 and 0.7 mm. Both are softer than graphite, so use a pencil with a gentle chuck such as Pilot's Color Eno pencil.
How many leads come in a tube?
It varies by brand and size: Nano Dia 0.5 mm holds 40, Ain Stein 0.5 and 0.7 mm hold 40 and 0.3 mm 15, Super Hi-Polymer from 8 (1.3 mm) to 30, and Color Eno 10. Check the count when comparing prices.
Does lead brand matter if the size is right?
Less than size and grade, but premium leads are smoother and break less. If you're happy with the Super Hi-Polymer in your pencil, a tube of Nano Dia or Ain Stein is a cheap upgrade to test.
uni Nano Dia mechanical pencil lead, 0.5 mm, 40 leads
Pentel Ain Stein mechanical pencil lead, 0.5 mm, 40 leads
Pentel Super Hi-Polymer mechanical pencil lead, 0.5 mm, 12 grades
Pilot Color Eno colored mechanical pencil lead, 0.7 mm, 10 leads, 8 colors