These are tension bolt washers made of genuine leather. They can be used to prevent tension bolts from loosening. Sizes are: Outer diameter: 12mm Inner diameter: 5mm Thickness: Approximately 2mm Color is brown. Due to the nature of leather, they are made slightly tighter to account for stretching. When installing, it will go on smoothly if you twist it on. Because they are genuine leather, there may be small scratches or color unevenness. Please understand. #Drums #DrumSet #Snare #Tom #BassDrum #TensionBoltWasher