# Gen 1 | Z-20 vs. Z-16 Z Slider Physical Differences

**URL:** <https://forum.onefinitycnc.com/t/gen-1-z-20-vs-z-16-z-slider-physical-differences/22370>\
**Category:** Z-20 Z Slider\
**Created:** [September 12, 2023, 7:54pm UTC](https://forum.onefinitycnc.com/t/gen-1-z-20-vs-z-16-z-slider-physical-differences/22370 "2023-09-12T19:54:16Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![OnefinityCNC](https://sea2.discourse-cdn.com/flex022/user_avatar/forum.onefinitycnc.com/onefinitycnc/32/7_2.png) [@OnefinityCNC](https://forum.onefinitycnc.com/u/OnefinityCNC)\
**Post date:** [September 12, 2023, 7:54pm UTC](https://forum.onefinitycnc.com/t/gen-1-z-20-vs-z-16-z-slider-physical-differences/22370/1 "2023-09-12T19:54:17Z")

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**What are the physical differences between Z-20 and Z-16 Z sliders?**  
How do I know which Z slider I have?

Please use the following pictures and information to identify which Z slider type you have.

1. **Gantry mounting hole position.**  
**Z-20** has 5 mounting holes on bottom and 4 on the top.  
**Z-16** has 3 mounting holes on bottom and 3 on top.

 ![Z-20 Vs Z-16 Mounting Holes](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/1/b/1bd9c300f42fab4cc1d95d692bd6af18ccb73651.jpeg)

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1. **Motor Size.**  
**Z-20** has a larger, high torque nema 23 stepper motor that is 75mm tall.  
**Z-16** has a regular nema 23 stepper motor that is 55mm tall.

 ![Z-20 Vs Z-16 Motor Height](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/6/0/603c9849d7cf4c6eb8ee1596b329f48a2c1629fa.jpeg)

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1. **Rod size. The Z sliders get their name by the diameter of the steel rods.**  
**Z-20** rods are 20 mm in diameter.  
**Z-16** rods are 16 mm in diameter.

 ![Z-20 Vs Z-16 Rods](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/e/1/e15d02ec998d3becc4fa608f88055cf18ef74e03.jpeg)

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1. **Ball screw size and thread.**  
**Z-20** ballscrew is 16/10. 16 diameter, 10 pitch. This allows for faster travel when compared to the z-16.  
**Z-16** ballscrew is 10/4. 10 diameter, 4 pitch.

 ![Z-20 Vs Z-16 Ballscrew](https://us1.discourse-cdn.com/flex022/uploads/onefinitycnc/original/3X/9/1/91e046777be829bb0f451261b3ab2ccba0dde0ca.jpeg)

This is useful when performing a reset on the BB controller and need to identify which z slider to select. [How To Reset The Configuration To Defaults (BB Controller) (FAQ)](https://forum.onefinitycnc.com/t/how-to-reset-the-configuration-to-defaults-bb-controller/2547)