TT Gear Motor 1 : 90 Mini DC 6V Gear TT Motor with Metal Gears for Robot Smart Car DIY RC Toys Electric Motor Gearbox(8pcs 1 : 90 TT Motor Blue)

I couldn't find any info in any product description, review, or answered question with regards to the size screw to use to secure a wheel to the rotor shaft on the blue metal-geared version.The answer: M2.5

6 out of 10 motors worked. Makes me wonder why there is such a high failure rate.

With the cost of 3D printers falling and being available for more households taking some of those idea's and adding a mechanical component to them is an excellent way to engage the thinking and creative part of both young and old alike. These gear motors are available in several different ratios and lend themselves to easy mounting and animation at a reasonable cost. A lot of the 3D model sites use this type of motor in various gearing to animate models and create mechanisms to power various devices. Both powerful and easy to connect to they are reasonable to have on hand to play with. They run from about 4V to 6V and there are a variety of battery holders to power them. This is a great way to bring the family in and create interests and hobbies to fuel their imagination

Exelente articulo

I had to order this in after I accidentally broke one that I got in a kit. And actually somehow these motors seem better quality than the ones I got that came in the kit. There was not difference in the gear box, the motors plastic and build quality was just better.

Got the job done