The 50002006 is a 10 inch Industrial Riser for RFID door portal antennas.  Can be used at the bottom of your installation to lift the bottom portal 10 inches from the floor.  Can also be used between the upper and lower portal sections to increase the height of the read zone.  Testing has shown that due to the fact that the portal antennas have vertical beam-width, using these risers does NOT cause any null in the coverage zone.