A Cat 1 lift pin would be 7/8" (0.875") so a ball for it should be just over that (which appears to be what you have).
A Cat 2 lift pin would be 1 1/8" and would be to large to fit through that ball.
(You appear to be measuring it against a Cat 1 toplink pin which would be 3/4". Toplink pins and lift pins are different diameters.)
