The Holdrite® HYDROFLAME™ PRO Series ''Sleeve Extensions'' (#HFPE1 - #HFPE6) are available to fit a wide variety of Sleeve combinations, from 1 in thru 6 in sizes. Each extension adds up to 4-3/4 in of height in 1/4 in increments. No coupling is needed! Height markings are shown on each part, in both U.S. and metric.