Genuine Merrill HBA750 brass hose reducer. This lets you use a standard hose on a Pipe threaded yard hydrant spout. Fits The Merrill M2000 Yard Hydrant and the Wellpro WM2000 Yard Hydrant. The center of the adaptor has a hexed portion that allows you to hook a wrench to it, to ensure adaptor is fit securely to the spout of the hydrant.
