These weld on fuel injector bungs are designed for do-it-yourself fabricators who make their own multi-port fuel injection manifolds. Manufactured from 6061-T6 aluminum bungs. They can be used in two different ways. The manifold can be drilled to16mm (5/8") to suit an O-ring seal or simply remove the O-ring and weld them directly to the manifold. Only fits 14mm O-ring style injectors.