Canon EOS-1D X Mark III Af Setting Manualbook page 72

Cross-type AF points
Use up to 155 cross-type AF points for
high subject capture performance.
f/2.8 and f/5.6 dual-cross AF points
f/4.0, and f/5.6 cross-type AF points
f/5.6 cross-type AF points
f/5.6 AF points (horizontal-line focusing AF)
Of the 191 AF points, you can use up to 155 cross-type
AF points with higher accuracy performance.The number
of cross-type AF points varies with the lens maximum
Based on an f/2.8 lens
155-point cross-type
(Of these, a single point
is dual-cross AF)
Based on an f/4 lens
55-point cross-type
Based on an f/5.6 lens
65-point cross-type
72