Measure the binocular before sizing the harness
Binocular harness sizing works best when you measure the binocular in the exact configuration you plan to carry, not when you assume every 8×42 or 10×42 needs the same pouch. Overall length can change with eyecup position, while hinge width, caps, a rainguard, and fixed connectors can change the space the binocular actually occupies. Measure