Impex high quality wall plugs are designed for use with all screw fixings in masonry and concrete. Main Material: The Expansion Tube is made of high quality plastic, environmental protection, injection molding, flexible, good toughness, impact resistance. Working Principle: The expansion pipe fully opens expanding on two opposing sides as you tighten the screw , increased holding power, and its anti-rotation structure design of the expansion sleeve, will not following the screw in the drilling rotation.