Medium Duty-Swivel/Rigid,6MM/Heavy Duty-Swivel/Rigid,5MM/Heavy Duty-Swivel/Rigid,Black Diamond-Swivel/Rigid,Run Steel-Swivel/Rigid,Zincification/Heavy Duty-Swivel/Rigid, Bracket thickness 2,3,4,5,6 mm. Surface sandblast, Zincfication. SB1-iron side brake.SC2-plastic double brake. !