For the SRAM RED eTap AXS 36T Max rear derailleur, the chain gap should be 5mm between the top of the upper pulley teeth and the tallest teeth of the largest cassette cog when using a 10-36T cassette, or a 10-33T cassette. The gap should be 12mm when using a 10-28T cassette. Rotate the B-Adjust screw until the appropriate gap between the upper pulley and the tallest teeth of the largest cog is attained. We also offer a chain gap adjustment gauge that will help set this distance correctly: 11.7518.100.000 – SRAM Rear Derailleur Chain Gap Adjustment Gauge for eTap AXS Cassettes 26-36T. See the eTap AXS Systems Manual for more information here.