Official NHL rinks are 200 feet long and 85 feet wide. Some rinks have slightly different perimeters. Fiberglass walls, called boards, surround the rink from the ice to a height of about 40 inches. Attached above the boards is a nearly unbreakable plexiglass rim to keep the pucks from flying into the stands. It is higher behind the goals since the pucks are most often shot into that area. The net is six feet wide and four feet tall. The nets are held on the ice by a four-inch plastic tubing which is inserted into the ice and the goalposts rest around the tubing.