TGB Slate BIABIt has to be BIAB the only builder gel everyone wants. Our darkest BIAB shade Slate is an off black with rich charcoal undertones in our revolutionary builder gel formula. Slate will give your clients stronger and longer nails in a bold and sophisticated finish that will make a statement. Apply. Top. Go! Black BIAB nails are something everyone's been asking for and now available in Original BIAB for long lasting results that last up to 5 weeks.