... /8" -20", for oil tubing and casing pipe 4.color black, blue, red, green 1. API Thread ... thread protectors are made of a threaded low density of high-density polythylene bumper,which absorbs the impact ... design of the protectors(steel shell and high density polyethylene bumper) insures the protector intergrity within ... 3/8",2 7/8",3 1/2",4",4 1/2",5",5 1/2",6 ... ",9 5/8",10 3/4",11 3/4",13 3/8",20",24"