This Zipp Vavle Extender Wrench set includes two 4 mm-and-5 mm combination wrenches to assemble removable valve cores from Zipp Tangente butyl inner tube and Zipp integrated valve extenders. Also works on other tubes and tubulars with removable valve cores. Sure, you can use a regular valve core tool, small adjustable wrench or pliers, but these wrenches allow a more precise installation of Zipp integrated valve extenders.