Pyramid Mandocello Strings, Green Set, 2 Sets Brand new, unused. Pyramid is the largest string manufacturer in Europe. They produce strings for guitars, violins, and of course, ethnic instruments from all over the world, claiming to have strings for everything. Optima strings, familiar to mandolinists, are made by a company that split off from Pyramid. Perhaps because of this, both Optima and Pyramid strings have a similar flavor. Differences between red and green: Red is round steel nickel wound - polished finish, while green is hexagonal steel nickel wound - polished finish. This is the same as Optima. I bought these out of curiosity, but I sold the instrument soon after, so they've been stored at home. I have multiple sets... please comment if you'd like more. Instant purchase is OK.