A magnetic element includes a conducting winding structure, first and second magnetic parts, and first and second side posts. The first and second magnetic parts have first and second central posts that are aligned with each other. The first side post is disposed on an edge of the first or second magnetic part. The second side post is disposed on another edge of the first or second magnetic part where no side post is disposed or the first side post is not aligned with. The conducting winding structure is sandwiched between the first and second magnetic parts. The first and second side posts are aligned with corresponding edges wherein no side post is disposed. Consequently, the overall height of the first and second central post is less than the height of the first or second side post and an air gap is defined between the first and second central post.