The Silvia's boiler is made of marine grade brass and has the largest volume (12 oz.) of any home machine in its class. This large volume produces the best steaming power and recycle time when brewing multiple espressos. The brass construction resists pitting and scale build up for long lasting durability.http://www.wholelattelove.com/products/rancilio-silvia-redesigned-v3-espresso-machine