This is an original Troy-Bilt replacement part. The O-ring is commonly found in yard equipment such as trimmers and edgers. This part is made of flexible plastic, and is used to cushion and seal the connection between the crankcase cover and the crankcase. Please be aware that there are different O-rings used in the machine. Refer to ...Read morethe parts diagram to be sure of ordering the correct part. You will require a screwdriver when replacing this part. This item is sold individually.