In 1998, in Prague, the FIS granted roller skiing an official FIS World Championships. On 30 August- 3 September 2000, these competitions took place in the Netherlands. Races have a variety of formats with different terrain. Formats include relays, sprints, team races, individual races and pursuit races. Terrain varies from relatively flat to hilly. On flat courses the speed can be as fast as 50 kilometres per hour (30 miles per hour). Average speed on flat tracks in World Cup races can easily be 30 kilometres per hour (20 miles per hour). As in regular cross-country skiing, the skiers compete in classic and freestyle. Helmets and protective eyeglasses in competitions are mandatory. World Cup and World Championships Like their cross-country counterparts, the Italian, Russian, Norwegian, Swedish, German and French rollers have been very strong in competitions compared to other nations since the beginning of competitive roller skiing. Note that World Roller Skiing championships are not officially sanctioned races by FIS or recognized sports governing bodies. Men So far, the World Cup and World Championships have been dominated by a few skiers. Successful roller skiers include Italian Alfio di Gregorio, who has won the World Games three times and World Cup four times; Russian Igor Glushkov, who has won the World Cup three times; and Frenchman Vincent Vittoz, who won the World Championships in 2002. Women Mateja Bogatec from Italy has been one of the most successful female rollers since the beginning of the FIS World Cup in 2000. Equipment Roller skis for classic and skate style skiing are used, as well as "combi" skis which may be used for either technique. Off-road rollerskis are a variation designed for rougher surface conditions. Classic style rollerskis usually have wide wheels to improve balance and better simulate classic ski technique. The wheel diameter is often less than 75mm to reduce the overall weight of the rollerskis. A ratchet mechanism is installed in either the front or rear wheel of each classic rollerski to allow uni-directional travel and simulate propulsion from classic ski strides on snow. The non-ratcheted wheel on each classic rollerski is free-rolling. Skate rollerski wheels are usually wide (similar to those used on inline skates) with a wheel diameter of 100mm. 105mm skate rollerski wheels are a less common standard. Pneumatic rollerski wheels are also available but are especially rare and require pneumatic specific rollerskis. Pneumatic roller ski wheels have significantly