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These stepper motors allow you to drive a dolly or other motion control accessory through the AUX port on the side of the TB3.
Both Motors have: Efficient Planetary Gear Drive 8 mm mounting shaft TB3 connector with strain relief (allows you to plug into the AUX port of the TB3 with no soldering or crimping. 27:1 is good for timelapse and is strong and can do vertical moves, but isn't fast. 5:1 is 5 times faster than the 27:1 so great for quick setups, but will stall with vertical component moves.