In these which is the correct preposition?

[varmaswathy81]

This device comes under the category of ab belts.

This device comes in the category of ab belts.

In these which is the correct preposition?

[englishhobby]

Both (but there are more results with "off" in Google)

[Route21]

Hi varmaswathy

As a NES, but not a teacher, I would use: "This device comes under the category of ab belts."

Hope this helps
R21

PS "This device falls into the category of ab belts." would also work for me.