This is an excellent product, particularly at this price. It does not come with instructions and I suggest blowing thru the valves to understand the operation before connecting it to water. The valves are adjustable on both the supply and return manifolds. They were closed when I received it which was confusing at first. The flow meters can adjust the flow and have a red locking ring that you have to pull down to turn them. Use plenty of Teflon tape on the NPT fittings, they are a little shallow and bottomed out on copper fittings. It connected to 1/2" PEX without any difficulties or leaks.Overall a great, well constructed product. Been in service for about 3 months with zero issues.