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Excellent Lego gear tutorial by Sariel: gear ratios, types of gears, best practices, etc. : r/lego
METAL GEAR SAHELANTHROPUS | Metal gear, Lego art, Lego worlds
File:Lego technic gears.jpg - Wikimedia Commons
Technic, Gear 24 Tooth (New Style with Single Axle Hole)
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Amazon.com: LEGO 16pc Technic gear SET : Toys & Games
Gears – Metal Technic Parts
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Self-locking Bricks | Gears Parts | Lego Gear | Model Building Kits - Self-locking Bricks - Aliexpress
Technic, Axle Metal Long, for Expert Builder Gears : Part pinpw2 | BrickLink
One LEGO 24-Tooth Technic Gears Dark Gray Part No 3648 1 Axle Hole | eBay