The G9 cap has a twin looped pin base with a 9mm space between the centres of each loop. The pins are 0.5mm in diameter. An alternative G9 style of cap uses two solid flat connectors, again with a 9mm space between centres and extending 4.4mm from the base. The G9 is the classic form of connector for a mains-powered halogen capsule, with retrofit LED and CFL versions also available. They are typically used in confined-space applications such as caravan lighting, boat lighting, desk lamps, small downlights, and projectors.
G9 Capsule (Halogen, LED, CFL).