... four steel grades (J55, K55,N80, L80 and P110), six sizes (1.9", 2-3/8", 2-7/8 ", 3 ... 2", 4", 4-1/2") of tube. API spiral steel pipe There are four steel grades (J55, K55,N80, L80 and ... P110), two categories (nonupset and external upset) and six sizes (1.9", 2-3/8", 2-7/8 ", ... ", 31/2 " and small caliber) of insulated tubing, and six items in total. The annual production capacity of high-vacuum ...