Distinctive features of Alpina vehicles are the fact that these models are literally "manu-factured", meaning "hand-made". The production process switches between fine tuning the engine, delivering it to the BMW plant, marrying engine and body there, bringing it back to Alpina for interior upgrade with Alpina's specific components, again all in a hand-made process that allows only limited production numbers. Besides engine and interior, Alpina also optimizes the transmission and installs steering wheel mounted button-shifters (called Switch-Tronic) on most cars, with paddle shifters used on the B4 S Edition 99. This has historic reasons, since Alpina was the first to mount shifting buttons on the steering wheel.