There is a mismatch in inside depth between the BCD adaptor and the flexible hose adaptor. It would be better if both have the same (= deeper) inside geometry.
BCD Adapter - An NRC O2 Analyzer accessory for oxygen analysis.
The T piece of your NRC analyzer is replaced by this adapter.
The adapter can then be plugged directly into your inflator port, allowing you to analyze your nitrox mix without having to unscrew the first stage.
It also protects the analyzer from splashing water during the measurement process.
Thanks to the additional nozzle function in the adapter, you achieve an optimal measurement result.