These are the correct tension springs for all Kahler bass and multi string guitar systems. Depending on your model, you may need between two and six springs. For most six string guitar tremolos, you'll need only two springs... either a standard tension set or a heavy tension set, depending on the string set used. String sets containing strings sizes between .008 and .048 must use these standard tension springs. If any string is larger than .048, you must advance to the heavy springs to compensate for the extra pull. Sold individually.