Genuine Mikuni jets provide the best replacement or calibration solution for your aftermarket or O.E.M. Mikuni carburetors. Do not use an imitation, nothing substitutes for O.E.M. quality and Mikuni jetting is guaranteed to be the exact size indicated because of high manufacturing tolerances. Large ROUND TYPE used in most Mikuni and others that originally came with 4/042 main jets. Common jets found on many of the larger motorcycle Mikuni carbs from the 70's and 80's. Equivalent to N100/604 Mikuni type series round jet with slotted head. Brass main jets are available in sizes 50 through 195 in increments of 2.5, in sizes 195 through 210 in increments of 5. Sold in a 4-pack.