The invention relates to a hearing protection earplug (10) to be worn at least in part in a user's ear canal, comprising a shell (12) having a outer surface individually shaped according to the measured inner shape of the user's outer ear and ear canal, and a functional member (20, 30, 120, 144, 220, 320, 420) engaging said shell in a manner so as to be movable relative to said shell between a first functional position and a second functional position, said shell and said functional member having been produced by an additive layer-by-layer build-up process and having an elasticity of between shore D85 and D65.