A choke includes a single-piece core made of a same material, the single-piece core having a first board, a second board, and a pillar located between the first and second boards, a winding space located among the first board, the second board and the pillar, wherein the pillar has a non-circular and non-rectangular cross section having a first axis and a second axis substantially perpendicularly intersecting with each other at a center of the cross section of the pillar, and wherein a circumference of the cross section of the pillar includes two arc edges, four first substantially straight edges substantially parallel to the first axis, and two second substantially straight edges substantially parallel to the second axis, each of the first substantially straight edges being a joint of and in direct contact with one of the arc edges and one of the second substantially straight edges.