20G refers to the gauge of the wire used - this wire is .036 inches in diameter, and is wound around a 3mm mandrel to achieve the proper size rings for a tight yet flexible chain.
Available in your choice of Argentium sterling silver, 14/20 yellow goldfill, 14/20 rose goldfill, or pure copper (or a mix of two together, see Duo Byzantine). Woven by hand from wire which is first cut into hundreds of tiny rings, then fitted together using needlenose pliers into this intriguing, complex and endlessly interesting ancient weave. Coordinating earrings and bracelet available, and made to order in any length you desire. (Price subject to change due to volatility of silver market - current prices based on $30/oz. spot price.)
Argentium sterling silver is a modern tarnish-resistant sterling silver alloy which modifies the traditional alloy (92.5% silver + 7.5% copper) by replacing some of the copper with the metalloid germanium. As it retains the 92.5% silver content of the traditional alloy, it is still referred to as sterling silver. (Wikipedia)