BARREL NUT,FLAT KNURLED NUT 1.ISO,ANSI,JIS,DIN,BS& ... :4.8 ,6.8,8.8,9.8.. BARREL NUT,FLAT KNURLED NUT,BARREL NUTS AND BOLTS . A good non-standard fastenerS manufacturer ... steel is SS201,202,302,304,316...copper is shiny brass , pure copper,such as H62,H65,H68...Aluminum is good ...