PE 26-28 PWK21-34 Carburetor Super Presisi  Repair Kit including following parts,

10pcs *  Main Jet 99101-357 M5 x 0.8mm: 105 / 108 / 110 / 112 / 115 / 118 / 120 / 122 / 125 / 130

11pcs *  Slow/Pilot Jet N424-21 M6*0.75mm: 38 / 40 / 42 / 45 / 48 / 52 / 55 / 58 / 62 / 65 / 68

1pcs *   PWK Holder Needle Jet 16164-169-0040

7pcs *   Jet Needle N427-46XXX With Needle Clip 0403-802-1000 (018-033): JFN / JFQ / JJD / JJE / JJF / JJG / JJJ

1pcs *    Holder Needle Jet N413-12A00:  24H

This fits:

 PE 26-28 carburetors

 PWK 21 24 26 28 30 32 34 carburetors.

Together with the mixer tube the jet needle regulates the composition of the mix in the partial load or half throttle ranges. The needles differ in terms of their colour, pattern, internal coating and dimensions. Each of the ranges has a specific effect on the composition of the mix. As a rule, the following applies: The bigger the jet, the richer the mix that results. The bigger the needle, the earlier the mix is enriched. 

The needle also has various clip positions, with which it is possible to determine its position. The higher the clip snaps into place on the needle, the deeper it is immersed in the mixer tube and the leaner the mix is in the half throttle range. If the needle is already in the lowest position and mix is already too rich (evident for instance if the Vespa sounds like a 4-stroke scooter when its slide is half open), then you should choose a thicker needle or a smaller mixer tube.