The present invention relates to a downhole plug with an expandable elastomeric packer (1) having two ends, surrounding a main section (25). The intended application of the downhole plug is for sealing wellbores and tubulars (4). At least one expansion ring (13) adjoins at least one of said two ends of the elastomeric packer (1), and at least one support ring (15) applies an axial force (16) in a longitudinal direction of the downhole plug. At least one of said two ends of the elastomeric packer (1) is made with a tapered surface. The at least one expansion ring (13) is made with a tapered surface configured in such a manner that the application of the axial force (16) in a longitudinal direction of the downhole plug leads to the simultaneous expansion of the elastomeric packer (1) and the at least one expansion ring (13).