The invention relates to a hearing protection earplug, comprising a hard shell (10) having an elasticity of from shore D 85 to shore D 65 and having an outer surface individually shaped according to the measured inner shape of the user's outer ear and ear canal for being worn at least in part in the user's ear canal, the shell comprising a filter cavity (12) having at least one orifice (20, 30, 40) into which a passive acoustic filter element (21, 31) is inserted for forming, together with said orifice, a passive acoustic filter. The invention also relates to a use of such an earplug and a method for manufacturing such an earplug.