The Type P valve trim Riobel 291085 is a pressure balance valve trim designed for use with gas and oil pipelines. It is made from brass and has a black finish. This valve trim is designed to reduce the pressure in the pipeline, allowing the flow of gas or oil to be increased or decreased. The Type P valve trim Riobel 291085 is a pressure balance valve trim designed for use with gas and oil pipelines. It is made from brass and has a black finish. This valve trim is designed to reduce the pressure in the pipeline, allowing the flow of gas or oil to be increased or decreased.