Number 2 pencils: What makes them so special?

It's a staple on everyone's back-to-school list, but why do we always use No. 2 pencils? They really are the best writing utensil for the job.
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They're at the top of every back-to-school list, but does anyone know why No. 2 pencils are so important?

Introducing Mini hexagon golf pencils that have an attached eraser which gives them a much classier look than typical golf pencils. This makes them

72 Pastel Pink Mini short half Hexagon Golf #2 Pencils With erasers Pre-Sharpened Made In the USA - Non Toxic Latex Free Express Pencils TM

Today is: National No. 2 Pencil Day

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This large size (13/32”) round No. 2 pencil is easy for small hands to hold making them ideal for children in the early stages of their writing

4ct My First Ticonderoga #2 Pencils with Sharpener

What Makes #2 Pencils So Special?

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My First Ticonderoga® Pencils at Lakeshore Learning

Pencil Review: Casemate and Pen+Gear No. 2 Pencil(s) – Polar Pencil Pusher

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What Makes One Pencil Superior to Another?

What makes a pencil a 'No. 2' pencil? What are the other kinds, and how are they different? - Quora

Noted! Extra Thick Graphite Mechanical Pencils - Set of 6 - OOLY

BIC Xtra-Sparkle No. 2 Mechanical Pencils with Erasers, Medium Point (0.7mm), 24 Pencils