This motor has 8mm output shaft…
This reminds me my sad story. I ordered the geared motors from Aliexpress. The model was 17HS13-0404S-PG5. And I received motors with that label!But later when I started assembling the robot… the motors proved 40mm long instead of 34mm in description! So they just could not fit inside. And the output shaft was 8mm.So I had to order the right motors from stepperonlinehttp://www.omc-stepperonline.com/gear-ratio-51-planetary-gearbox-with-nema-17-stepper-motor-17hs130404spg5-p-140.htmlI did not know about this shop before, but now I highly recommend it. Fast shipping, good quality. If I only had known, I’d ordered all motors from them..