EBC pilot jets are precise, clearly marked and reliably gauged using pin gauges, and accurate to one tenth of a thousandth of an inch. All jets are flow calibrated and extremely accurate in terms of fuel flow rate as stamped. Keihin 424-21 pilot jets measure 18.7mm long. High precision brass pilot jets for Keihin carburetors using 424-21 pilot jets. Kit contains 1 piece each jet sizes 35 thru 80 for a total of 19 jets.