Made in Europe A+D, steel wire core wound with precision-rolled stainless steel G+C, steel wire core wound with precision-rolled tungsten Tension Soft 57.8kg/127.4lbs, medium 58.6kg/129.4lbs, strong 60.1kg/132.5lbs The original Cello series is based on a solid steel core and is supplemented by an E string wound with precision-rolled aluminium. The A and D strings are wound with a special precision-rolled stainless steel flat wire, while the G and C strings are wound with tungsten.