 What's the difference between B-flex and color building bases on the market? Color building bases are in fact two-in-one products. They are a base and a builder, and they require a bit of constructing, they are not so self-leveling, and they also will require a separate gloss because they're not shiny. Oftentimes they also contain acid for better adhesion, and of course that means that they are a little bit more difficult to remove and they can damage the nail plate. B-flex is an all-in-one product, so base builder, tone, and gloss, and it's also very fast. It's extremely self-leveling, doesn't require filing, so it's really going to be your time saver in the subtle. By the way, it's acid free.