The Uniweld G30D Replacement Brass Case Compound Manifold Gauge is a replacement brass case compound manifold gauge for use with the Uniweld G30D compound gauge. This manifold gauge is made of brass and is designed to help you measure the compound pressure in your engine. The Uniweld G30D Replacement Brass Case Compound Manifold Gauge is a replacement brass case compound manifold gauge for use with the Uniweld G30D compound gauge. This manifold gauge is made of brass and is designed to help you measure the compound pressure in your engine.