galvanized steel pipes tubes isi marked in random length of 4 to 7 mtrs screwed at both ends socketed at one end and other end screwed protected with plastic protector nominal bore dia 20 mm medium class sockets shall also be isi mark material and specification 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 quantity