This is one of the most unique valves I've come across.  The handle and ball rotate 360* in the seat.  The passages of the ball itself are drilled through as well as a single perpendicular 'tee' port.  This gives you four different flow options.  As expected, the valve can flow from A to C or from B to C, but it can also be set to flow from A to B, blocking off C or it can have all 3 ports open, A to B and C.  This is a great feature for cleaning and/or draining your system.  Made from 304 stainless steel and has 1" tri clover flanges on the connections.