This product is developed with reference of GB/T17880.2-1999 standard with the further improvement as per our customer’s actual requirements and our comprehensive market research; it is ribbed on both surfaces of round body and flange to grip better against rotation. This product is most commonly used and has become one of our flagship products. After continuous development over years, wide range of different sizes of this product are available from size M4 up to M12 and from size 6# to 1/2UNC as per American standard as per the specifications below. Large inventory has been buiIt to ensure the high customer demands are met.