The P stands for precision, .50 MOA, = minute of angle means at 100 meters, each click of the windage knob moves the point of impact 1/2" left or right. The sight also has new notches above the round apertures for faster CQB engagements inside of 50 meters and also for long range 500-600 meter.
Designed for and selected by Crane Naval Surface Warfare Center; and currently under contract for use by Special Operations Forces.

When folded down, height is only .610 from the top of the receiver to the top of the sight in folded position. Notice the added feature of the captivated nut to prevent loss.