Our M16 Magazine Upgrade kit for 30 round magazines includes a next generation high performance spring and the new generation green follower. The springs are made of chrome silicon wire. Chrome silicon wire has 1000 times more memory than music wire or 17-7 stainless wire, which are the type of wire in current M16 magazines. Unlike other springs ours are not inclined to take as set. In addition our springs have a zinc phosphate (Parkerizing) finish. This finish provides 72 hours of corrosion protection in a salt spray environment. The followers are slightly different than the followers designed and manufactured in the last century. This results in smoother and more reliable feeding. Our followers are manufactured from Nylon-6 with chopped glass fibers added. This results in a follower with increased hardness, toughness, and lubricity. These followers are also more stable at both cold and hot temperatures than your old followers. Each kit which includes one spring and one follower. For 30 round magazines.