Dura-Grind® Stainless Steel Dounce Tissue Grinders provide a rugged alternative to glass Dounce tissue grinders. Smooth pestle action requires less effort than glass tissue grinders. Precision-machined of No. 316 stainless steel. The mortar has a flat bottom allowing it to stand upright. Single pestle and mortar are supplied as a matched set; they are not autoclavable.