Abstract: A poke through includes a tube assembly having inner and outer tube sections that are slidably telescopically disposed together. A lip protrudes from the outer end of at least one of the tube sections. A cup is selectively and removably disposed on one of the tube sections. The cup has a body plate and a flange. A portion of the lip on the tube section on which the cup is disposed engages the front surface of the body plate. In one embodiment, an adjustable plug has a plurality of selectively removable rings. The adjustable plug fits inside one of the tube sections to seal and insulate the poke through both before and after the poke through is in use.