Akron Brass Oscillating [3531] Flange for Brass Monitor 4" Flange x 4" Flange Unpainted. The Style 3531 is capable of flows to 1500 gpm at an oscillation range up to 165° and is compatible with most Akron Brass manual monitors. Its unique maintenance-free polymer bearing design, high quality material construction and superior performance make it the ideal choice for a long-term, low service solution for protecting your hazardous and harsh environments.