To be more specific, our standard coupler size is 1/2", but you can get 3/8" for no extra. Standard is 1 male/1 female, but you can get 2 male or 2 female for no extra.
Some people like flat face couplers, which are commonly found on skid steers. You can order the grapple with FF couplers for $75 extra.
For reference, here is all 3 types:
3/8"(left), 1/2"(center) and flat face(right)
And a more specific reference of each:
3/8" male....Pioneer 4010-3P 11PT

3/8" female...Pioneer 4050-3P
1/2" male...Pioneer 8010-4 1/2-14NTPF

1/2" female...Pioneer 4050-4 1/2-14NTPF
Flat Face Male...18NW Parker FEM-502-8FP

Flat Face Female...120W Parker FEM-501-8FP-NL
Travis