Big Bertha is the name given by Callaway Golf to a number of its lines of golf clubs. The name was chosen to evoke the famous German Big Bertha howitzer. The original Big Bertha driver was launched in 1991. At the time, its design was considered highly modern and a radical departure from older drivers: it was crafted entirely of stainless steel and the head had a volume of 190 cm3 (12 cu in). Most other drivers were still made of persimmon wood and had smaller heads. (By way of comparison, many drivers of recent years have head sizes up to the USGA legal maximum of 460 cm3 (28 cu in) and are made of more exotic materials such as titanium.)