These plastic tube inserts are designed to knock into the ends of tubes or pipes to act as feet or end plugs and in most cases are available in a choice of colours, check the colour/finish drop downs for options.
As with all our inserts, they're listed as you would buy the tube so it's Outside Dimensions x Wall Thickness / Gauge Size, or if you're trying to match up to a sample, the key dimension is the head size.
The tops of the inserts are designed to sit flush with the outside of the tube whilst the shank has flexible horizontal ribs to suit a multitude of tube walls, in a range of both metric and imperial sizes.