GHS Santana Big Core Signature Set Pure Nickle Wrap Light 10 1/2 -48 Carlos Santana was introduced to Big Core Strings by his Guitar Technician, Rene Martinez. He has continued to use them and the result is beautifully realized in his new Signature Series. Rene Martinez has been one of the nation"s leading experts in guitar maintenance and repair since 1972. Rene worked at Dallas Texas" famous Charley"s Guitar Shop From 1976 through 1985.