Delrin inserts for conical roller stones. They are sold in a set of 4. Two pieces are needed for each stone. Choose the delrin inserts for the model you have. They are different for ECGC-12SL, ECGC-12SLTA, ECGC-12SQSS and ECGC12SSRD. If you are not sure about the model you have please contact us for help.