The present invention provides a sealing plug for blind installation in a suitable hole (50) thereby to plug and seal the hole, which sealing plug comprises a sleeve (2), a nut stem (4) having a shoulder (8), and a head (6) at least part of which is radially enlarged with respect to the remainder of the stem; the nut stem being of a material which is harder than that of the sleeve; the nut stem being internally threaded; whereby, when the sealing plug is inserted in a suitable hole, with the sleeve entirely within the hole, and increasing force is applied to the stem with respect to the sleeve, axial compression is applied by the shoulder to the sleeve material abutting it, thereby causing the sleeve to deform and expand radially outwardly to engage with the wall (52) of the hole.