API, API 5L, ASTM A106-2006, ASTM A53-2007, ASTM A210-1996, GB/T8162, Gb/t8163, BS 1387, DIN 1626, DIN 1629/4, DIN 17175, JIS G3452-2004, JIS G3457-2005
1.Black varnish painted or oil painted, 2PE.3PE on the surface.
2.Plain,square cut or beveling ene by caps.
3.In hexagon or triangle buddle with steel strips.
4.Other as the customer's requires.