A tubular passage for poured concrete decks has an intumescent tube held in a two-part, clamshell base by a bottom clip. A first tube engages the base's top to clamp a funnel shaped, diaphragm seal to the base. The first tube has spaced, radially extending, parallel ridges at predetermined distances from the base. Longitudinal channels separate the ridges. An extension tube has inward extending lugs passing along the channels to engage various ridges when rotated to fix the passage length. The extension engages the base bottom for corrugated deck supports. A cap with repositionable, locating filaments closes either tube.