Abstract: A ring including an annular mounting flange portion and an annular main body portion formed integrally with and spaced axially from the mounting flange portion is provided. The mounting flange portion includes structure for its rigid mounting on and support from an outer peripheral portion of a high speed rotating component and the main body portion includes a cylindrical seat surface having a groove formed therein and extending continuously peripherally thereabout and opening laterally outwardly through the seat surface. A closure ring defining a cylindrical closure surface is supported from the body portion with the closure surface abutting and sealingly secured to the seating surface on opposite sides of the grooves whereby to close the latter. The closed groove has movement dampening liquid disposed therein and fluent weight bodies are also disposed within the groove and their movement within the groove is dampened by the movement dampening liquid.