uxcell 20 Pcs Black Silicone O Ring Seal Washers 21mm x 15mm x 3mm Product Name : O Ring Seal;Outside Diameter : 21mm / 0.83" Inner Diameter : 15mm / 0.59";Thickness : 3mm/ 0.12" Material : Silicone;Color : Black Weight : 12g Package Content : 20 Pcs x O Ring Seal