Abstract: A one-piece, molded elastomeric grommet for mounting in a hole that extends through a support panel for passing a member through the support panel has an elongate tubular portion defining a passage that extends from an inlet at one end of the tubular portion to an exit at an opposite end of the tubular portion. An umbrella portion surrounds the tubular portion and has a forward end that is integrally attached to the tubular portion so as to form an open ended acoustic chamber outwardly of the tubular portion. A mounting portion at a rearward end of the umbrella portion comprising a forward mounting flange and the umbrella portion includes a collapsible wall having a substantially uniform thickness and an undulate shape in a circumferential direction to facilitate insertion of the forward mounting flange through an undersized hole in a support panel.