The Aston Martin DB4 Competition, which is also sometimes referred to as the Lightweight, was a non-factory race car offering created by notable Aston Martin specialist R.S Williams and Aston Engineering. Inspired by the DB4 GT, but built using a Base Model DB4, the DB4 Competition is a series of race cars featuring a stripped-out interior and inline six engines ranging from 4.2L to 4.5L in displacement. Each of these DB4 Competition cars is unique in nature, but these cars are common enough that the Aston Martin Owners Club refers to these cars unofficially as the Series 6 DB4.