Automatic chain oiler, its a little reservoir with a tube that runs down the swingarm to the rear sprocket. Theres a little needle there that applies the oil to the chain. No dripped on driveways, no rolling the bike around, no oiling, no BUTCHERED FINGERS !!!!!! ( That hurts every time i look at it!!!!!) Just fill it up once a month and go. Absolutely the best add on for chain driven bikes ever invented. My chain and sprockets show virtually no wear after 19K miles because they are continually oiled.