body-checking was only allowed in the defending zone in international hockey Several other rule changes were implemented in the early 1970s: players were required to wear helmets starting in 1970, and goaltender masks became mandatory in 1972. In 1992, the IIHF switched to using a playoff system to determine medalists and decided that tie games in the medal round would be decided in a shootout. In 1998, the IIHF passed a rule that allowed two-line passes. Before then, the neutral zone trap had slowed the game down and reduced scoring. The current IIHF rules differ slightly from the rules used in the NHL. One difference between NHL and IIHF rules is standard rink dimensions: the NHL rink is narrower, measuring 61 m × 26 m (200 ft × 85 ft), instead of the international size of 61 m × 30.5 m (200 ft × 100 ft) The larger international size allows for a faster and less physical style of play. Another rule difference between the NHL and the IIHF rules concerns how icing is called. In the NHL, a linesman stops play due to icing if a defending player (other than the goaltender) is not behind an attacking player in the race to the end-zone faceoff dots in his defensive zone, in contrast to the IIHF rules in which play is stopped the moment the puck crosses the goal line. The NHL and IIHF also differ in penalty rules. The NHL calls five-minute major penalties for more dangerous infractions of the rules, such as fighting, in addition to the minor and double minor penalties called in IIHF games. This is in contrast to the IIHF rule, by which players who fight risk a game misconduct & major penalties. Beginning with the 2005–06 season, the NHL instituted several new rules. Some were already used by the IIHF, such as the shootout and the two-line pass. Others were not picked up by the IIHF, such as those requiring smaller goaltender equipment and the addition of the goaltender trapezoid to the rink. However, the IIHF did agree to follow the NHL's zero-tolerance policy on obstruction and required referees to call more hooking, holding, and interference penalties. Each team is allowed to have between 15 and 20 skaters (forwards and defencemen) and two or three goaltenders, all of whom must be citizens of the nation they play for. Banned substances The IIHF follows the