Ink refill container and ink refill system

An ink refill container configured to refill ink into a printer that has:

• an ink tank chamber;
• a needle that communicates with the ink tank chamber to introduce the ink into the ink tank chamber;
• and a pair of recesses arranged on both sides across the needle,
• the ink refill container comprising:
• a container main body including an ink chamber configured to contain the ink;
• a cylindrical portion having an ink outlet configured to allow the ink to flow out from the ink chamber;
• a pair of projections extending in a center axial direction of the ink outlet and configured to be inserted into the pair of recesses;
• a male threaded portion located lower than the pair of projections in a state where the ink outlet faces upward;
• and
• a cap having a female threaded portion formed in an inner circumferential face thereof and configured to screwed with the male threaded portion,
• wherein a slit-like clearance is formed between each of the pair of projections and the cylindrical portion.