Difference between AR3 and AR2 is that each motor in AR3 have rear shaft and mounting holes for encoder.
Here is the youtube video show how to build a AR3 robot by yourself OPEN SOURCE LOW COST ROBOTS
If you expect to get AR3 motors only, please click here to buy.
More details for parts i..
Package includes:
2 x 14HS20-1504S--NEMA14 Stepper Motor 40Ncm
1 x 17E13S0404MB4-200RS(17E13S0404MB-200RS)(17LS13-0404E-200G)--NEMA17 Stepper Motor (34mm max) with integrated lead screw 200mm T8x8
1 x 14HR07-1004VRN--NEMA14 36mm round pancake Stepper Motor with 10 tooth spur gear
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