tl;dr: ASUS's Oxiis E250G1 is a friction-drive motor that clamps onto a conventional bike's seat post to convert it into an e-bike, delivering 250W rated (500W peak) power with a 158Wh removable battery good for ~50km in eco mode. It fits most bike types (16-29" wheels, tires up to 60mm, seat posts 25.4-34.9mm), weighs 3.7kg, charges in 2 hours via 100W USB-C PD, and offers three assist modes controllable via app.