Adapters to connect a power tool (like a cordless screwdriver) to Technic axles, allowing you to power up your models without having to buy expensive motors and batteries. 

Included are two adapters, one in the shape of a Technic axle, like the old motors, and one in the shape of an axle hole, like the newer Powered Up and Power Functions motor. Choose the one that better fits your model. 

The setup works great with the small Bosch IXO, which has around 200 RPM, very similar to Technic electric motors. Other electric screwdrivers may vary. Of course it also works with manual screwdrivers, as long as they are compatible with ¼'' hex bits. 

Note that even if their rotation speeds are similar, power tools usually provide more torque that small motors, so be careful not to overstress the parts. These attachments are best for sets which work continuously, but don't have motors included, like the big Loop Coaster set. Such sets usually also have torque-limited gears or chains to protect against damage if anything gets stuck.