Probable component of the tectonic-like complex (also named MKS complex), a complex localized at the transition zone of primary cilia (PubMed:27646273, PubMed:25447994, PubMed:27577095). Has a role in ciliary structure and function (PubMed:27646273). Probable component of the tectonic-like complex (also named MKS complex), composed of B9d1, B9d2, Cc2d2a, Mks1 and tctn. Localizes at the transition zone (TZ), a region between the basal body and the ciliary axoneme (PubMed:27646273). In spermatocytes, localizes in the transition zone and the migrating base of the spermatid ciliary cap (PubMed:25447994, PubMed:27577095). Co-localizes with the tectonic-like complex (PubMed:27646273). Expressed in chordotonal neurons in the antennae (at protein level) (PubMed:27646273). Expressed in spermatids (at protein level) (PubMed:25447994, PubMed:27577095). Simultaneous knockout of B9d2 and tctn is viable and does not show sensory behavioral defects (PubMed:27646273). Males produce motile sperm and show only slightly reduced fertility (PubMed:27646273). Sperm flagella show weakly ultrastructural defects including broken and disorganised structure (PubMed:27646273). Length of the transition zone is decreased and recruitment of the tectonic-like complex compromised (PubMed:27646273). Belongs to the B9D family.