EK G1/4 plug with o-ring. To tighten the plug you will need 6mm allen key.

EK-Quantum Torque Plug w/Cover 10-Pack - Black is a premium Quantum G1/4" plug set of 10 pieces for closing the unused ports on your water cooling equipment. Ideal for when you don’t want G1/4" plugs to be seen.

EK-Quantum Torque Plug - Nickel is a premium Quantum G1/4" plug for closing the unused ports on your water cooling equipment.

EK-Quantum Torque Micro Plug - Black is a premium small-form-factor Quantum G1/4" plug for closing the unused ports on your water cooling equipment.

EK-PLUG G1/4 Acetal - Black (10 pack) is a simple pack of ten black acetal G1/4" plugs with o-rings.