Kullerbu 彩色球

Fascinating to see how the water inside makes it heavier than a normal ball — my kid loves watching the little plastic pieces swirl around as it rolls down the track.

My toddler grabbed it immediately just to shake it and watch the little plastic balls swirl around inside the water. It’s surprisingly durable for how much he throws it across the room, and the rolling motion is more entertaining than I expected for a simple ball.

The water-filled core makes it heavier than a normal ball, so it rolls slower and more predictably on the track, which is actually great for younger kids. The little colorful balls floating inside are a fun visual bonus, though I wish the outer shell were a bit more durable for rough play.