Where did the phrase "balls of steel" originate from? : r/AskReddit
Is there an accepted female equivalent of having 'balls of steel'? If not, what should it be? - Quora
I wore balls in my vagina for my birthday and it wasn't as fun as
What Are Steel Balls And How Are They Used
Ball (bearing) - Wikipedia
What is equivalent of the phrase “Balls of Steel” but for women? - Quora
Electrostatics - Pith Balls | Electricity and Magnetism | Physics Demos | Physics | College of Science and Engineering | Seattle University
Large Steel Balls, Uses? - Problem Solving - I Forge Iron
Businessman Try To Cut the Chains that Tied His Leg To Large Black Steel Metal Balls in Meaning the Debt. Stock Vector - Illustration of determination, character: 148436973
Balls-of-steel Definition & Meaning | YourDictionary
Why do people put steel balls on their pickup trucks and vans? - Quora
Benefits and Uses of Casting Steel Ball
Balls of Steel with Arctic Core review - The Gadgeteer
How steel balls are made - Boing Boing
balls of steel meaning and pronunciation - YouTube
Balls-of-steel Definition & Meaning | YourDictionary
What is the meaning of "I've got balls of steel"? - Question about English (US) | HiNative
Baoding Balls: You'll love this hand exercise to improve hand strength — Jamber
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Manufacturing process of casting steel ball
Balls of Steel- great mission, but the product left us cold | Daddy Mojo
I've got balls of steel"是什麼意思？ - 關於英語(美國)（英文）的問題| HiNative
props to this guy
