Holley Alcohol Jets are specially designed to work only with Holley 4150 HP carbs O-80542, O-80535, O-80498. The unique metering blocks used with these carbs are designed to accept the physically larger size of this main jet. Two lengths are available: a ''standard'' length jet and an ''extended'' length jet. The standard length jet can be used with a stock, unmodified float; the extended jet is like a jet with a built in slosh tube, and must be used with a specially-modified ''notched'' float, for clearance.