Evolution Gun Works Barrel Link Kit 6 Pieces Chromoly Steel Black. Set of 6 includes: #0 #1 #2 #3 #4 #5. Machined from heat-treated 4140 chromoly steel and then sent for bluing. Specifications for Evolution Gun Works Barrel Link Kit 6 Pieces: Manufacturer: Evolution Gun Works Color: Black Finish: Chrome Fabric/Material: Steel Features of Evolution Gun Works Barrel Link Kit 6 Pieces #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 Package Contents: Evolution Gun Works Barrel Link Kit 6 Pieces Evolution Gun Works 10300: Barrel Link Kit 6 Pieces Chromoly Steel Black