What Are These Rough Bumps on the Backs of My Upper Arms?

I've seen the lotion for it, and I'll say personally, it works great. 3 days of use and my skin is smoother. But what are the bumps? The been there for half a decade and they haven't gone away until recently me using the lotion? I've seen that it's called KP or something on the lotion container.
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+1 y
The bumps do not hurt, and yes I know what the lotion is, to clarify the comments.
What Are These Rough Bumps on the Backs of My Upper Arms?
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