From the Super Mario Wiki
A Middle Ring (also known as a Checkpoint Ring) is a ring of light in Super Mario World 2: Yoshi's Island, Yoshi's Island: Super Mario Advance 3, Yoshi's Island DS, and Yoshi's New Island. It appears partway through most stages and serves as a checkpoint of sorts. If a Yoshi loses a life after passing through one, he can restart at the point of the Middle Ring. Also, passing through a Middle Ring will increase Yoshi's Star Power by ten (giving him one and ten more seconds) and turn all on-screen enemies into stars.
Despite their name, Middle Rings are not always placed in the middle of a stage. Some can be found at the very beginning, or not until near the end. A few stages even have multiple Middle Rings and there are always a couple before boss fights.
Names in Other Languages
- ^ http://www.youtube.com/watch?v=BHms7CddrdM