Main text This is the final report of CCT-K7.2021 key comparison of water-triple-point (TPW) cells. The primary objective of CCT-K7.2021 was a comparison of the participant national realizations of the TPW temperature. Each participant laboratory selected one of its TPW cells for use as a transfer cell, directly compared it against its national reference and delivered it to the pilot (NRC). The pilot then compared all transfer cells against two NRC reference cells and, finally, each participant laboratory retrieved its transfer cell and directly re-compared it against its TPW national reference. The initial measurements at the participant laboratories were started in April 2021. The final measurements at the participants' laboratories were completed in September 2022. The final report was approved by the CCT WG-KC in April 2023. The adaptive weighted average procedure was adopted to compute the Key Comparison Reference Value (KCRV) and the degrees of equivalence (DoEs) were reported for the participant laboratories. The maximum difference between two transfer cells was 92 μK with a standard deviation of 26 µK (almost a factor of two improvement compared to CCT-K7 results (2002-2004). The maximum difference between two TPW national realizations was 111 µK, with a standard deviation of 28 µK (improvement similar to the one reported for the transfer cells). While the pooled distribution of CCT-K7 results was bimodal, indicating the presence of two different sub-populations (the population of laboratories that referred to ocean water definition and the population of laboratories that did not consider it), the pooled distribution of CCT-K7.2021 results was no longer bimodal, but slightly asymmetrical, indicating a more harmonized approach to water isotopic corrections. To reach the main text of this paper, click on Final Report . Note that this text is that which appears in Appendix B of the BIPM key comparison database https://www.bipm.org/kcdb/ . The final report has been peer-reviewed and approved for publication by the CCT, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).