Mercedes-Benz's costliest convertibles are two-seaters with a power-retractable metal hardtop. Four models are offered. New for 2007 is the SL550, it replaces the SL500 and has a 382-hp V8 vs. 302 hp. Carried over are the high-performance SL55 AMG with a 510-hp supercharged V8, the SL600 with a 510-hp twin-turbo V12, and the SL65 AMG with a 604-hp twin-turbo V12. All have automatic transmissions: a 7-speed on the SL550, a 5-speed on the others. All include a manual floorshifter, with AMG versions adding performance programming and steering wheel shift buttons. Standard are traction/antiskid control and Mercedes' ABC active suspension designed to reduce cornering lean. Also standard are "by-wire" antilock brakes that can modulate brake pressure to each wheel. All include head- and torso-protecting side airbags, driver knee airbag, and a rollover bar designed to deploy in an impending tip. Also standard are navigation and assistance systems; adaptive cruise control is optional.