The invention relates to a feed-through member (1) which is to be mounted in a wall element or floor element and comprises a tube element (2) that includes a first (23) and a second (24) tube element section. Said tube element sections (23, 24) can be moved relative to one another in the conducting direction (21) in such a way that the length of the tube element (2) is adjustable, a blocking mechanism (26, 32; 51, 61) being provided which at least partly prevents the tube element sections (23, 24) from moving when same are in the relative positions.