galvanized steel pipes tubes isi marked in random length of 4 to 7 meters screwed at both end s socketed at one end and other end screwed protected with plastic protector nominal bore dia 15 mm mediu m class sockets shall also be isi mark drawing no mat spec is 1239 pt 1 2004 rev 6 amend no 6 of june 2021 for tube is 1239 pt 2 2011 rev 5 amend no 3 of march 2016 for socket and is 554 1999 rev 4 amend no 1 of oct 2009 for screw warranty period 30 months after the date of delivery galvanized