20mm CLOSED (blank - blanking) Wiring Grommets
Quantities: 1, 5, 10, 20, 50
Size refers to the diameter of the hole the grommet fits
These are generally used in electrical installations to Blank off holes were wires or conduit would normall pass or connect through metal or sharp edges.
20mm is a common size for metal pattress boxes used in domestic electrial installation