A rubber base coat is a flexible UV base coat for gel polishes, designed to give extra strength to flaky, brittle, thin, or splitting nails. It can also be used to add some structure to the natural nail, giving it extra durability and a nicer shape.
Rubber bases have a higher viscosity and they come in a variety of different nude shades.
Rubber base coats are designed to be used together with a UV gel product, most usually a gel polish. They are not strong enough to be durable by themselves, so applying regular nail polish over them will not last on someone’s natural nails.