4 bolt hole quantity four additional holes on 1.312 dia bolt circle, no 10-24unc-2b-0.438 dp 0.152 dia-0.562 in. min to 0.593 in. max dp csk 90.0 deg min to 100.0 deg max to 0.214 in. min to 0.234 in. max dia-equally spaced; two additional holes 0.107 in. min to 0.114 in. max dia