CSS auto padding top and bottom to always have the height covered

As in this test page https://play.pianohub.it/
I’m using three carousel sliders with two navigation arrows

If you hover over either the nav arrows, you’ll see that this div covers only a portion of the picture height, while I need it to span top to bottom.
I’m using this CSS

.arrow {
    font-size: 18px;
    padding-right: 7px;
    padding-left: 7px;
    background-color: rgba(22,22,22,0.29);
    color: #ffffff;
}

I tried to use padding:auto for top and bottom but it is not a thing. I should fix it by counting the needed pixel but it wouldn’t be responsive.

How can I set automatic padding?

>Solution :

If the list-container and the arrow have the same father, you can set:

height: 100%;

so the height of the arrow will be as 100% as the father