As others have said, I couldn't bleed, so I couldn't even bleed my system with the POS installed. Unfortunately, due to the weather, I had to wait too long to start my disc brake rebuild, so for me there are no returns/refunds. However, I disassembled the valve and found a broken and twisted o-ring on the piston and I had to pry it out of the exhaust port with air pressure. O-ring replaced, still no passage from inlet to outlet, don't waste your time or money.