Abstract: Base and cover members of a vacuum filter having walls each terminating with an annular bead are sealably joined together by a flexible annular joint. The joint has a median part defining, with an inner flange and a first rounded outer lip, an annular cavity in which the bead of the base member is tightly gripped. A second thinner and more flexible rounded outer lip fits over the bead of the cover member and has a terminal skirt portion which resiliently bears against its wall. The cover member can be removed by outwardly bending the second lip while the joint remains fitted on the base member.