Mercedes-AMG GmbH has been a wholly owned subsidiary of the Mercedes-Benz Group. Development of the product range AMG started off by designing and testing racing engines. It expanded its business into building custom road cars based upon standard Mercedes cars. AMG initially produced a range of unofficial upgrade and accessories packages mainly for the Mercedes-Benz R107 and C107 (1971–1989 SL roadster), Mercedes-Benz W116 (1972–1980 S-class), Mercedes-Benz W123 (1976–1985 E-class predecessor), Mercedes-Benz W124 (1984–1997 E-class), Mercedes-Benz W126 (1979–1992 S-class), Mercedes-Benz R129 (1989–2001 SL roadster), and Mercedes-Benz W201 (1990–1993 C-class) models. During the early 1980s and up until 1990, AMG offered a variety of engine performance packages, alloy wheels and styling products as an entirely independent company from Daimler-Benz. In 1990, AMG signed a co-operation agreement with Daimler-Benz, and AMG options and cars were then offered in Mercedes-Benz showrooms; in 1999 Daimler AG, then known as DaimlerChrysler AG, bought the controlling share of AMG and made them part of the official Mercedes-Benz line-up. Typical AMG performance enhancements, which the buyer could custom order, included increased engine displacements (5.2 litre, 5.4 litre), performance top ends with port and polished heads and intake, lightened valve train, and more aggressive cams. The DOHC 32V engine had also just been developed and was the pinnacle of AMG performance. A Getrag five-speed manual transmission could be ordered from AMG, and Mercedes had not offered a manual transmission V8 since the early 1970s. The performance wheels offered during the same period were 15-inch or 16-inch ATS AMG Five Spoke Road Wheels, commonly referred to as Pentas. Penta was actually a UK-based company that supplemented the high demand for the AMG wheel at the time with a replica and only a very slight styling difference, but they were not made or endorsed by AMG. The genuine AMG wheels were often coupled with an AMG performance suspension package that included uprated and lowered springs, and re-valved shock absorbers. Another popular cosmetic upgrade were the AMG body kits. These ranged from subtle front spoilers to aggressive Wide Body kits for the W126 coupes (reaching more than $700k on the classic market in 2022). Other options included Recaro seats, smaller diameter steering wheels, instrument clusters, chrome delete option (all brightworks colour-coded or painted satin black), refrigerators, shift knobs, hi-fi stereo systems, custom upholstery and enhanced interior wood packages. The release of the AMG Hammer sedan in 1986, based on the W124 E-Class,