The original U•BASS strings, the Road Toad Pahoehoe U•BASS Strings are Kala's signature, light tension "black rubber" strings: a proprietary polyurethane blend that gives your U•BASS a distinctly round tone with a huge amount of low-end. These Road Toad Pahoehoe U•BASS Strings are recommended for players in search of an upright tone with a great deal of flexibility and maneuverability. Available in 4-Strings and 5-String sets