This air corrector jet acts as the holder for the Starter Jet on Weber DCOE carburetors. Note that on older Italian-made DCOE carbs, this holder was one piece with the starter jet. The later 2-piece style separates the air jet from the starter jet. Size 150 only. Sold individually, 2 required per carburetor. Starter jet not included.
Note that different calibrations of this jet (and the starter jet) were available back when DCOE carbs were supplied with a cold-start enrichment device or "strangler" choke, to suit different driving conditions. Because these carbs are no longer offered with a cold-start device (and because Weber realized that the majority of users simply removed it), the calibration has been standardized. Eliminating this variable reduces the possibility of spoiling an otherwise perfect jetting.