The Phoenix Contact SK 5/3,8:FORTL.ZAHLEN 11-20 marker strip is a self-adhesive marker card designed for use with terminal blocks. It is horizontally labeled with consecutive numbers from 11 to 20, making it ideal for identifying and organizing circuits and connections. These marker strips are commonly used in industrial automation, electrical panels, and control systems to ensure proper identification and maintenance of terminal blocks. The white color provides excellent contrast and readability.