The 15/20 was introduced by BSA in 1910. This model featured rear-wheel drive and a 4-speed manual transmission. It was available in several body configurations, including torpedo, tourer, and landaulette. The engine was a 2.5L inline four-cylinder, capable of generating between 15hp and 20hp. This model symbolizes BSA's transition from a weapons and bicycle manufacturer to an automobile producer. It also helped lay the groundwork for future collaborations and developments within the BSA-Daimler group, contributing to the growth of the British automotive industry before the First World War. The BSA 15/20 was produced until 1926.