The Corvettes at the Nürburgring were all U.S. production-spec vehicles. The only modifications were the safety equipment recommended by the track. This includes a roll hoop, full containment race seat, fire extinguisher, and a six-point safety harness. All three set lap times for the Prototype/Pre-Production category, since the ZR1 and ZR1X are not sold in Europe and the Z06 was a North American variant. Inevitable footnote: 1 Do not use summer-only tires in winter conditions, as it would adversely affect vehicle safety, performance, and durability. Use only GM-approved tire and wheel combinations. Unapproved combinations may change the vehicle’s performance characteristics.