Standard Pack = 1 piece(s). Drill ExtensionsCollet Type Drill Extension System4 IN & 9 IN Extension use ColletsAccommodates 1/16 IN thru 5/16 IN drillsSlim profile gets into places that other Collet type extensions cannot accommodateThreaded type Collets eliminate the need for bulky Collet nutsIt's easy to change Collets, no special Wrenches requiredA low cost system for difficult to reach spots