Used in flat roofs of any construction. The adjustable extension sleeve permits adjustment from a minimum of 1-1/4 in (32) to a maximum of 4 in (100), easily accommodating up to 2-3/4 in (70) of varying insulation thicknesses. The positive threading allows smooth perimeter movement and circumferential support of the top at any adjusted elevation. Large low profile dome provides sufficient free area for quick drainage of rainwater and protection against debris.