This is an elasticated fabric band with a plastic button embedded in it.
A simple task of putting elasticated stockings on to one of them was made difficult because only one was allowed to be cared for by the carer looking after them.
They are now often not from silk, and consist of a fabric over an elasticated core.
It has the buttons on the left flank, elasticated wrists and a mandarin collar, and is quite similar to a chef's uniform.
These were made in a variety of materials including heavy denims, silks, and even elasticated fabrics.
The closures at waist, neck, wrists and ankles are all elasticated to help retain body heat and moisture within the garment.
The new version even dropped the elasticated side straps in favour of seat-belt style straps with buckles as these were found to be more durable.
Some designs use elasticated webbing or bungee cords around the bladder to constrict the bladder when not inflated, although there is dispute as to the wisdom of this addition.
