... gearbox -size: Ø36 mmx(25-52)mm--metal housing material -Gears in steel - Plastic gears are available for noise reduction ... shaft<0.3mm-Pinion gear hole:Ø3.175mm-all reduction ratio: 1 stage reduction: 1/3.7 , 1/5.2 2 ... 1/264 ,1/369 ,1/516 ,1/721 5 stages reduction: 1/699 ,1/977 ,1/1367 ,1/1911 ,1/ ... ,1/3736 One of all models: PG36-50.9K reduction ratio: 1/50.9Numbers of stage:3efficiency :73%(3stages) ...