Machined from heat-treated 4140 chromoly steel and then sent for bluing.
#3 is standard link size.
0 is for Accurail guns, when the rails have been moved down.
#0 - .263" center to center
#1 - .268" center to center
#2 - .273" center to center
#3 - .278" center to center industry standard G.I. Spec
#4 - .283" center to center
#5 - .288" center to center
