A coupler to couple a D-ring from a harness to a fall arrest device connector provides walls to guide and contain the harness webbing whilst allowing it to move freely (reducing webbing wear) and does not necessitate the removal of the coupler, connector, or D-ring as may be required for harness size adjustment. The coupler has a circular passageway which runs through the length allowing a shaft of the connector to couple to the part whilst maintaining 180 degrees of swivel. The coupler also has a groove which runs along the length to fit onto a central bar of the harness D-ring. The design is such that, during a fall, should the device break, the webbing will remain securely coupled to the D-ring of the harness.