An elastic ring, defining an inner opening, an outer contour and an annular bearing surface between the inner opening and the outer contour. The ring is deformable between a rest position and an insertion position in which the inner opening has a diameter greater than its diameter in the rest position. The ring is also elastically biased towards the rest position. The ring includes at least three strands passing through the ring, each strand having a first end and a second end positioned on the outer contour, the inner contour of the opening being defined by a portion of each strand and having a pseudo-polygonal shape.