What is the opposite gender of bulk?

"Bulk" is a noun that refers to a large quantity or mass of something. It's not a gendered term. Therefore, it doesn't have an opposite gender.

It seems like you might be looking for a word related to "bulk" that has a gendered counterpart. For example, if you were thinking about the word "male", the opposite gender would be "female".

If you can tell me what you're trying to express, I can help you find the right word!