A plug with infinite order and some exotic 4-manifolds

Abstract: Every exotic pair in 4-dimension is obtained each other by twisting a {\it cork} or {\it plug} which are codimension 0 submanifolds embedded in the 4-manifolds. The twist was an involution on the boundary of the submanifold. We define cork (or plug) with order $p\in {\Bbb N}\cup {\infty}$ and show there exists a plug with infinite order. Furthermore we show twisting $(P,\varphi^2)$ gives to enlargements of $P$ compact exotic manifolds with boundary.