Many types of ClearSpan High Tunnels are available from Growers Supply. They enable growers to harvest more and extend their growing seasons. The 42'W Colossal High Tunnel provides more space for growing and tending crops. It is constructed from 14 gauge Allied Gatorshield structural steel tubing. Sidewall height is 4 feet and ridge height is 15 feet. It is covered with a single layer of 6 mil four-year greenhouse film.