For use on Kala U-BASS Thundergut is a special very dense and elastic-plastic blend developed at Aquila which grants better performances than common polyurethane and silicon rubber strings available in the market. Thundergut strings do not present excessive stretching during tuning. They can therefore be installed directly on the peg tuner avoiding the boring task of manual pre-stretching that has to be done for the common polyurethane or silicon rubber strings. The Thundergut string's surface is not particularly sticky as silicon rubber, these strings are not too slippery when touched and are not so easy to go out of tune as in the case of the polyurethane strings. These have a maximum scale of 24 inches.