The "I"-shaped cameras mounted on top of the engine covers, seen on selected cars from 1995 to 1997, were made mandatory for each car in 1998, and changed to a more aerodynamic "T"-shaped camera; this design has remained largely unchanged since. Mid-season technical changes "X wings", a pair of tall aerodynamic appendages mounted at the front of each sidepod and first seen on the Tyrrell 025 in 1997, were banned before the Spanish Grand Prix. The teams that used them in 1998 were Ferrari, Jordan, Prost, Sauber, and Tyrrell. Driver changes Gerhard Berger retired at the end of 1997 after fourteen years in F1, leaving a vacant seat at Benetton. The team also opted not to renew Jean Alesi's contract, so the Frenchman signed a two-year deal to join Johnny Herbert at Sauber. As their replacements, Benetton signed Giancarlo Fisichella from Jordan, and Alexander Wurz, who had substituted for Berger for three races (including one podium finish) in 1997 when his fellow Austrian was ill. Jordan replaced Fisichella by signing 1996 World Champion Damon Hill from Arrows to partner Ralf Schumacher. To fill his seat, Arrows secured the services of Tyrrell's Mika Salo alongside Pedro Diniz. Tyrrell also parted ways with Jos Verstappen in the off-season, despite Ken Tyrrell wanting him to stay. However, new owners British American Tobacco preferred to hire Brazilian Ricardo Rosset, who had briefly raced for the now-defunct Lola team in 1997. They promoted test driver Toranosuke Takagi to fill the second seat. Verstappen returned to F1 midway through 1998 with Stewart, while Lola's other driver, Vincenzo Sospiri, instead found a home in the IndyCar Series. Prost retained Olivier Panis, but dropped second driver Shinji Nakano and replaced him with Jarno Trulli. Trulli had started 1997 with Minardi but then substituted for Panis when he broke his leg at the Canadian Grand Prix. Meanwhile, Nakano joined Trulli's old team, Minardi, to replace his retiring countryman Ukyo Katayama. He was partnered by rookie Esteban Tuero, who was promoted from a testing role as he was preferred to the outgoing Tarso Marques. Marques would eventually return to F1 in 2001, also with Minardi. Williams (Jacques Villeneuve and Heinz-Harald Frentzen), Ferrari (Michael Schumacher and Eddie Irvine), McLaren (David Coulthard and Mika Häkkinen) and Stewart (Rubens Barrichello and Jan Magnussen) all retained their 1997 driver line-ups. Mid-season driver changes The only mid-season change was at Stewart. Jan Magnussen was dropped