This SAFO alerts operators to the recent release of Technical Standard Order (TSO) TSO-C172, Revision A, with an effective date of December 22, 2015. Specifically, the Federal Aviation Administration (FAA) is drawing attention to the note in Appendix 1, which states the prohibited use of the D6 end fitting. This prohibition is due to risk of self or inadvertent disengagement, whether or not the D6 end fitting is under tension.