Hockey is a sport of finesse, tenacity and speed, all contained in the talent of the players. Hockey can be played on any surface, although ice and hard rubber "roller turf" are the two main fields currently played by professionals. Although these two variations of hockey may seem the same to some, they actually have many differences. Roller hockey contrasts with ice hockey in several ways. While the playing surfaces are the most obvious difference, the number of players, periods and skates also vary. The most obvious difference between the two sports is their playing surface. Ice hockey is played on a three-inch layer of ice cooled to about ten degrees Fahrenheit. Roller hockey is played on a two-inch layer of a plastic-rubber composite. Both types have specific advantages and disadvantages. The roller "turbo" almost never needs repairs while the ice must be resurfaced between each period. Ice is generally known to be a faster surface, but a good argument is the fact that players and equipment have more to do with speed than the surface. Hockey wouldn't be hockey without the players. The NHL is famous for its five-on-five play. Roller hockey, on the other hand, is four-on-four. Strategically in ice hockey two players remain primarily on defense while the other three are sent forward on offense. In roller hockey, however, with only two forwards on offense, one of the two defensemen must move to join the attack in order for teams to have an effective attack. While it causes a little headache for defensive players, having four players on the floor allows for more open ice skating and play. This also has a downside though, four players doing the work of five can be boring for the players leading to the need for shorter periods. By league standards, ice hockey consists of three to twenty minutes with a fifteen-minute intermission after the first and second periods. Roller hockey plays periods of four to fifteen minutes. The first and second periods are separated only by a five-minute break, the second and third by a fifteen-minute interval, and finally the third and fourth by another five-minute break. Overtime periods are also different. Overtime in ice hockey lasts five minutes. If neither team scores a goal within these five minutes, the match is declared a draw. Roller hockey has a similar five-minute overtime period, but if the tie remains unresolved, teams participate in a shootout to determine a winner..