The MSU has an inlet flow on one of the header side ports and filtrate flow out the casing side port. The other header side port is meant as a flush/test port. When using the MSU to filter tap water, you can improve filter life by flushing out the accumulated particulate inside the hollow fibers. This port also allows integrity testing of the filter with an air holding test. Once you do the air test, the end port allows the air to escape during re-priming. For RO use, these features may not be needed and the header cap could simply be plugged. The MSU is 16 inches long by 3.5 inches in diameter. The MSU is currently being tested and the filter and pricing will be available shortly.