【C.M.】 Slide Ring Curtain Rings Inner Diameter 38mm Black Suitable for poles up to 30mm in diameter. Pack of 30. Brand new, unused. Black Pack of 30 Outer Diameter: 46mm, Inner Diameter: 38mm, Length 57mm (See the diagram on the left for specific dimensions) Material: Steel Approximately 8-10 slide rings are needed per 100mm of custom-made curtain. These curtain rings are suitable for poles up to 30mm in diameter. Please check the size of your pole before purchasing.