I recently discovered Pacific's very rare and hard-to-find Tournament Pro Bull Gut string, which Pacific describes as the as most exclusive and highest quality natural gut string. It is also the world's most expensive tennis string: 70 Euros ($94 USD) for one pack. It is available in 1.25 mm (16) and 1.30 mm (16L) gauges. There is no recommended tension listed on the back of the pack, but the product description mentions each set containing specially selected fibers from 6 to 8 bulls, hence the high price. As the name implies, it is not just a natural gut string, it is a natural gut string made exclusively from bull gut. This string should not be confused with the Prime Gut Orange Bull Fiber string, which is just the Prime Gut string, with an extra orange bull fiber strand wrapped around it. Pacific's Bull Gut was nowhere to be found. I contacted three different online tennis stores, and Tennis Warehouse Europe was the only one store willing and able to order this string for me. Both gauges are now currently in stock at TWE. I recently got three packs of this string: I will write a review of this string in a week or two, when I get it strung up in one of my racquets.