The antenna consists of 5 collinear dipoles that radiate a narrow beam that is electronically steered into the approach region. The design provides a substantially reduced critical area which is the smallest of any image glide slope antenna in the world and maximizes airport capacity and construction opportunities. Capture-Effect (M-Array) Systems require three elements. Null Reference (NR) and Sideband Reference (SR) Systems require two elements. Factory test data is included Mounting hardware not included.