The rear-wheel drive Boxster is offered in two trim levels: Base and S. The Base is powered by a 255-hp 2.9-liter flat six-cylinder engine, while the S boasts a 310-hp 3.4-liter flat six-cylinder engine with direct fuel injection. Both are mated to a six-speed manual transmission; Porsche's PDK seven-speed double-clutch gearbox, including manual shift mode and steering wheel paddles, is optional. Boxster Base trims are equipped with 17-inch alloy wheels, LED tail lamps, leather seat trim, air conditioning, cruise control and a CDR-30 audio system with MP3-compatible CD player; S trims add 18-inch alloy wheels and an upgraded sound system. Standard safety features on both trims include Porsche Stability Management (PSM), four-wheel anti-lock disc brakes with brake assist, front and side seat-mounted airbags with a curtain airbag for head protection, and fixed roll-over protection bars. Popular options include a limited slip rear differential, Bi-Xenon headlamps with dynamic cornering lights, ventilated seats, Bluetooth wireless connectivity and a universal audio interface that can control external audio sources such as an iPod or USB stick. Following a significant refresh last year, the second-generation Porsche Boxster carries over unchanged for 2010.