Abstract: A packer member including a plurality of corrugated rings, particularly for sealing the annular clearance between the casing and tubing of an oil well. The packer is carried upon a collar presented by a member coupled into the tubing, and axial compression of the packer flattens the corrugations, expanding the rings radially so that such tightly fit with the inner wall of the casing by either penetrating it or being distorted against the inner wall, and at the same time the axial compression makes a tight fit between the inner edges of the rings and the collar on which they are supported. The packer may include a stack of corrugated rings alternately positioned with rings of harder and softer materials, and occasional robust rings may add stability.