This is the "Original and the Best" as recommended by JP and is an invaluable piece of equipment especially when swinging larger coils. The lower ball coupling sits over your belt and the upper section attaches to where your bungee was, with the bungee then clipping into the D ring. The weight from the detector/coil assembly is transferred to your hip, making detecting a more pleasant exercise.
This is a "Must Have" if you have shoulder or back problems as it eases the load on your shoulder. Ladies are able to swing much larger coils than normal and we blokes can swing the "big" coils for extended time periods.
There are 3 lengths to suit different bodies (16", 18" and 20"). Simply measure from your belt to your shoulder, subtract 2" and that is the size that will suit you.