External Coolant Flow Tap Adapter.
MRK#1 Straight-Shank Tap Holder (Coolant Through) | 1 in.
MRK#2 Straight-Shank Tap Holder (Coolant Through) | 1 in.
MRK#3 Straight-Shank Tap Holder (Coolant Through) | 1-1/2 in.