They typically will call a mouthpiece like a 'head joint' of a flute. So you have a bass sax mouthpiece with protective cap, a 'suit' or 'set' - like a 'suit of clothes', a set of associated items. I don't see why this is so perplexing.
Milandro has it right - over-reliance on automated translation software.
Knowing the Chinese characters and their common translations what this looks like is a package of a mouthpiece, ligature and cap.
"head blowing mouth" = mouthpiece
"whistle card" = metal ligature
"protection cap" = cap
Your big challenge is what kind of horn this piece fits. I doubt it is for a Bass sax. I will write the seller in Chinese and ask.
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