The Defender™ Solar Panel Bird Spikes come pre-assembled with 304 grade stainless steel pins (each strip being 33cm long). Once installed, these pins act as bars that do not allow the pigeons or birds to push through. As solar panels and solar water-heating systems can be installed on various roof tile shapes, be it a flat tile or a pantile (s-shaped), different heights of posts may be needed to fully protect the sides and prevent birds from crawling underneath. The Defender™ Solar Panel Bird Spike comes ready assembled in a choice of 4 different metal post heights to accommodate the varying spaces that need pigeon proofing. 75mm, 100mm, 125mm, 150mm. Prices are per strip.