Push-on Retainers (Pushnuts, Press Nuts, etc.) are in the group Industrial Hardware. Industrial Hardware is another of the wide range of products sold to manufacturers along with fasteners. These items, which are often used with fasteners to assemble machinery and products, can vary from items as simple as O-Rings and Oil Seals, through grease fittings and grommets, to torsion springs and sprockets.
Pushnuts are available on the FCH Network with Imperial/US diameters that range from #1 to 3 and with Metric diameters that range from M2 to M14.