API, API 5CT, API 5L, API 5DP, ASTM A106-2006, ASTM A53-2007, ASTM A210-1996, ASTM A312-2007, ANSI A213-2001, ASTM A199, GB/T8162, Gb/t8163, DIN 1626, DIN 2391, JIS G3463-2006, JIS G3444-2006
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.