Abstract: A compact, easily used, high quality sealing plug for use with ultrasonic testing equipment which incorporates a single annular body with an indented diaphragm portion, two lips, an annular vertical wall extending upwardly from said indented diaphragm portion of said single circular body with two annular lips extending outwardly therefrom, one at the upper end of said annular wall and the other therebelow so that when said seal is in use, the upper lip will maintain a position above the insulation material in which the seal is placed, while the lower lip will be below said outermost surface, both lips counteracting each other to maintain tension therebetween and the present invention from becoming unintentionally dislodged from its location. Alternative embodiments of the present invention are also disclosed which include alternative lip arrangements for alternative sealing needs and desires.