Cheers, Chris. Gut and Silk 900 are from Aquila, based on Pujol's measurements, said to have been used by Tárrega. They're good, but I prefer Damian's gut if I can get some. The silk-core strings, wound in silver, are quite dead sounding, and are prone to breaking overnight. Aquila recommends tuning them down overnight, which I do, but even then I'll find one broken of a morning. So, as a set they are expensive. I found this set in a drawer from about four years ago. My go-to alternative would be the Savarez White Card set, which are cheap, or the Pepe Romero antiquated set, I forget what they are called, and they are impossible to get in the UK.