PF2W is a digital flow sensor for water or coolant.  This is a legacy sensor, refreshed in 2009 as PF3W.  This is the remote version of PF2W7, with a display.  The mounting bracket is integrated into the body, while the M12 lead wire is optional.  PF2W5 can be paired with a PF2W200 or PF2W300 remote monitor to display instantaneous or accumulated flow values.  An optional analog output is also