Twinwall plastic is a generic term given to an extruded polymer product. Two layers of polymer are connected by flutes to form a sturdy sheet of material which has a wide range of uses. Most twinwall sheets are nominally transparent to allow light transmission, but colored or translucent sheets are also available. The airspace in the cellular space between sheets provides insulating properties, and additional layers of material can be extruded to provide two or three insulating cells, at the cost of light transmission.
Greenhouses use twinwall panels in lieu of traditional glazing due to the plastic panels' greater efficiency.