Model A: Rest of the Z.T. family so called ZERO TOLERANCE because once adjusted it grants the minimum possible movement of the rest support arm. This rest allows you to raise and lower the rest support arm, to increase and decrease the stiffness of the magnet, and to change the angle of the rest arm to your arrow diameter. Its shape fits perfectly to the W&W, PRO ACCENT, INNO, TF APECS, CXT, NEXUS, EXCEL, SEBASTIAN FLUTE, and GREENHORN risers Model C: Rest of the Z.T. family so called ZERO TOLERANCE because once adjusted it grants the minimum possible movement of the rest support arm. This rest allows you to raise and lower the rest support arm, to increase and decrease the stiffness of the magnet, and to change the angle of the rest arm to your arrow diameter. Fits perfectly on most of risers.