The REV Robotics 90 Tooth Plastic Gear fits on a 5mm hex shaft. The hex shaft interface completely eliminates the need for expensive hubs or using potentially unreliable set screws. Gears 45 tooth and larger have a hole pattern on an 8mm pitch enabling easy mounting directly to REV Extrusion, REV Brackets, and other 8mm pitch systems. All REV motion products have a uniform 15mm width to make quick design swaps fast and easy.
Warning: Gears from other building systems may have a very similar tooth profile but are not an exact match. It may be possible to use the two gears systems together successfully in some situations, but it is not recommended.