An RFID registration apparatus for registering units comprising RFID tags. The registration apparatus comprises: a detector space defined by a top, a bottom and four vertical sides including a first vertical side and a second vertical side, wherein the second vertical side is opposite the first vertical side; a receiver adapted to receive a number of units and be placed inside the detector space; a first antenna configured for reading RFID tags by emitting and receiving electromagnetic radiation within a first frequency range; and at least four plane reflector surfaces. Wherein a first primary reflector surface and a first secondary reflector surface span a first angle, and a second primary reflector surface and a second secondary reflector surface span a second angle. The first angle and the second angle are in the range of 70-140 degrees.