Eyeglass Frame Grips--Hinge Tighteners - Rubber hinged rings that provide flexible tension for a secure and comfortable fit. Simply slip a frame grip up each bow over the hinges. The resulting flexible tension will give a tight, comfortable fit. Pins and screws in these hinges cannot become loose or fall out. 24 Pairs of rings in each package - 48 total rings. Each ring is approximately 4mm inside diameter. Please measure your bows to make sure that these will fit.