The Holley jet assortment kit is the professional way to track-tune your Holley carburetor for top performance. This kit consists of two (2) each of thirty-six (36) different jet sizes, ranging from #64 to #99. The jets are contained in a plastic case that is designed to keep them separated and make them easily accessible. Jet sizes selected will give the broadest range of adjustment and tuning for most performance carburetor applications.